Long-used large ship now shakes itself apart - WTH?

[psychogre]

Using KAS, I constructed a large mothership in orbit that transports a collection of ore-mining/support landers.  I've taken this ship to multiple planets, setting up the mining base on multiple moons and planets.  All the landers return and are re-docked to the mothership before moving on to the next place.  I've been doing this over a year in real-life, nearly five Kerbin years.  See the screenshots below.
I exited the game one day at a point where the ship is nearly back to Kerbin (minus a few comm sats left in place) - about 14 days out from an interception.
Resuming my game the very next day, suddenly the whole ship starts wobbling and gyrating, like a bunch of hula dancers on pogo sticks that are tied together with bungee cords.  After some point, explosions ensue, and various remaining portions of the ship drift off in different directions.
Thinking at first it was some error in the loading of the KSP game, I restarted it at a previous savepoint.  Same damned thing happens - usually starting as a quiver, then gradually increasing in magnitude, until the explosions..  Restarted again, picking another savepoint even further back - still happens.

My version of KSP (1.7.3.2594 Windows) has not been upgraded in over a year.  I also have Breaking Ground (1.2.0).  Primary mods, all also unchanged in over a year : Kopernicus, KAS, KIS, Snarkiverse, EasyVesselSwitch).  I've never used 'autostruts' at all, plus there was significant on-orbit construction.

The forum entries discussing similar wild behaviors have suggested turning off the reaction wheels, adding autostruts, etc.  Tried them, no change.  I found the WorldStabilizer mod - installing that had no effect.
My ship has over 500 parts, plus many landers connected with docking ports.  My tests with adding 'autostruts' was done only on a limited number of key parts, but with no discernable change.

At this point, I have only two ways of stopping the gyrations - either 'time warp', or undock the miner/ISRU lander that seems to be the part that consistently breaks apart first.  I obviously can't timewarp through the rest of this ship's return to Kerbin, and removal of one of the landers severely unbalances the use of the ship's engines (needed for the Kerbin orbit insertion).

Still looking for a solution - any other suggestions to try?
I've looked beyond KSP, for any other system changes that occurred between the 'normal' and 'gyrating' behavior.  I found that there were Windows 10 updates applied in between - though it was only Office updates.  I also had Dell updates, but I can't find a record of what those were; BTW my Nvidia graphics card driver was last upgraded a few months ago.  Is there any way to determine if something was upgraded that affected the Unity engine?
 

[linuxgurugamer]

How about undocking and then redocking the miner?

[Okhin]

Have you try to quickly warp / unwarp (not physics warp, classic warp)? It usually resets all the wobbling that I can feel after some loading / entering in physics range and stuff (I suspect it odes that by negating all forces, then recomputing them, reducing phantom forces and resonance).

[VoidSquid]

I once had a similar issue, my orbital station shaking itself to oblivion after I docked a ship to it. Found out it was the type to Autostruts (in particular for the docking ports), after I changed them to Grandparent Part, the issue was gone.

Edited September 7, 2020 by VoidSquid

[psychogre]

16 hours ago, linuxgurugamer said:

How about undocking and then redocking the miner?

Tried that multiple times, still happens.  Even tried docking at a different port, still happens, though the wobbling took a bit longer to start up.

16 hours ago, Okhin said:

Have you try to quickly warp / unwarp (not physics warp, classic warp)? It usually resets all the wobbling that I can feel after some loading / entering in physics range and stuff (I suspect it odes that by negating all forces, then recomputing them, reducing phantom forces and resonance).

The wobbling starts up again after unwarping.  No matter how many times I do that...

 

8 hours ago, VoidSquid said:

I once had a similar, my orbital station shaking itself to oblivion after I docked a ship to it. Found out it was the type to Autostruts, after I changed them to Grandparent Part, the issue was gone.

I've never used Autostruts and only recently learned that there are different types.  Any recommendations on which type of struts to apply to which kind of ship parts?  My feeling is that it would not be useful/necessary to add them to every single part (>500) of the ship.

[OHara]

One other common cause is SAS, if the 'control from here point' is far from the strongest control actuators (RSC or reaction wheels). 

Maybe after redockings you were left with a control point sensor that wobbles one way, while the reaction wheel is wobbling the other, as part of the hula dance.  Then SAS tries to slow down the wobble of the sensor, but does so by commanding a torque on the reaction wheel that instead increases the amplitude of the hula dance.

[Wobbly Av8r]

I've had the same problem on a less stressful level - a rover with a claw. I got the type of feedback loop that @OHara describes and couldn't figure out why my rover went nuts after attaching the claw to pod... the pod with its own reaction wheels and orientation, but no electricity until I attached to it... Once I disabled the reaction wheels of the scrap pod, all was well.

Something in your 500+ part vessel is creating a ressonance... and your problem - maybe something that wasn't powered before.

[Spricigo]

17 hours ago, psychogre said:

or undock the miner/ISRU lander that seems to be the part that consistently breaks apart first.  ... ... removal of one of the landers severely unbalances the use of the ship's engines (needed for the Kerbin orbit insertion).

Maybe I'm just trowing ideas thee, but did you tried to substitute that miner for something different (less parts, similar mass, just to keep the balance)? 

 

[psychogre]

The thing that irks me the most is that this ship, with all of its various landers docked to it, was totally stable when I exited the game one day, and was unstable when I resumed it the next day.
It had been stable throughout the multiple planetary body visits over several Kerbal years.

There was no state change (what was docked to what, torque rod settings, etc) to trigger this behavior; even loading up a earlier (stable) savepoint became unstable.
I'm still thinking there was some change that was external to the KSP program itself and my savepoints, ie some dll dependencies that changed the physics behavior. 

[king of nowhere]

i have no ideas for a solution, but i can say that i also had things that always worked suddenly stop working. like a docking port connected to a robotic arm that always connected nicely, until at some point it caused bugs every single time it attached. or a plane that flew straight, then i try it again one week later and it tilt to the side almost immediately.

 

actually, i have a suggestion: reinstall the game. this game sometimes pick up glitches, and some of them can be fixed this way. my docking port bug got fixed like this. my plane, unfortunately, not.

[psychogre]

On 9/7/2020 at 7:57 PM, king of nowhere said:

actually, i have a suggestion: reinstall the game. this game sometimes pick up glitches, and some of them can be fixed this way. my docking port bug got fixed like this. my plane, unfortunately, not.

I had high hopes a reinstall was going to resolve the problem; I finally got a chance to try that this weekend.  Well, it did change the behavior, but not for the better - the pogo/hulu wobble of the ship still happened, and then the gyrations continued even after undocking the miner lander.  Egads!

I returned to experimenting with the Autostruts again.  This time I set them on the ISRU units of both miner landers, to 'root'; less wobbling, but still the lower part of that lander eventually shook itself off (instead of breaking apart at the top of the ISRU).  That inspired me to set the autostrut to 'root' on the main engines of the miner landers, and also for the engines of the adjacent science landers - basically the furthest part out.  That calmed everything!  As a test, I proved that disabling the autostruts caused the wobbles to return.

Now I can return to completing the flight back to Kerbin!  Thanks for all the suggestions!