Phantom Acceleration after staging to SWERV in low orbit.

[i208khonsu]

• KSP Version 0.1.1.0.21572
• Operating System and version  (Windows 10, Windows 11) Windows 10
• CPU and GPU models, any other system information which could be relevant  Ryzen 2920X - RTX 3080
• Description of the bug.  
  • Expected Behavior When burning the SWERV engine I should get the posted thrust.
  • Observed Behavior I receive thousands of times the thrust after staging to the engine even with zero throttle. This thrust continues until my AP extends just beyond Kerbin SOI
• Steps to Replicate Launch a craft to 100km, begin orbital insertion. stage to SWERV when bottom stage runs out of fuel.
• Fixes / Workarounds (if known..) Unknown. Has happened both times I've attempted to launch this rocket.
• A list of ALL mods.  If the list is long, please consider using a spoiler window. None
• Other Notes / Screenshots / Log Files (if possible..)
  No timewarp was used (which I see other bugs reporting odd acceleration under timewarp which I believe this is NOT associated with). Here's a video demonstrating the second attempt of launching the rocket. More or less the same thing happened with the first launch. In the instant I stage to the SWERV I go from 570m/s to over 1000m/s. This speed then quickly increases to 15000km/s. The craft workspace can also be downloaded here: https://drive.google.com/file/d/1I6qrfYkEp48P3mnpauSGV9XoiChm8-4J/view?usp=sharing

 

Edited March 19, 2023 by i208khonsu
Calling out additional details of the video example.

[i208khonsu]

I think this may be caused by the fact that I disabled the fairing around the SWERV engine, or that the placement of the SWERV on the decoupler changed between the initial release and Patch 1.

I tried enabling the fairing, but when doing this only the top half of the fairing was being placed around it, so I detached and reatached the decoupler which fully then placed the fairing around the SWERV. Interestingly the rocket was quite a bit harder to control after this. Perhaps I need some fins around the lower stage now, but making no other changes than getting the fairing fully on I was able to get the spacecraft into a stable orbit twice (the first more sloppy than the second).