Setting the mass of parts to 0 seems to cause issues with the thermal calculations

[Yemo]

I modded parts to have 0 mass, to have the same behaviour as the previous physics significance flag, removing mass for the part, not adding it to the host part.

There seems to be a bug with the thermodynamic system.

Instead of ignoring parts having the physics significance flag for thermal puposes (thus physics), it seems to be unable to handle massless parts correctly (ie by ignoring them).

This is a post of the DeadlyReentry modder, discovering this problem:

Edit #2

To anyone affected by the issue involving massless parts, I will elaborate further, I can't consider that to be a bug in Deadly Reentry because the root cause is not in Deadly Reentry. As I've said before, DRE does not implement its own thermodynamic system. It modifies the existing stock thermo system that was introduced in KSP 1.0 and it relies on the existence of certain data called PartThermalData (that's the actual name of the class, I'll refer to it as PTD) and it is generated for every single part that exists in KSP regardless of whether it is marked as 'physicsless'

The absence of the PTD is what was causing the nullref errors for some players before. So I checked to make sure that the PTD was actually present (and not null) before moving forward with further thermal related code. But I was logging the error and that caused performance killing lag for players so I removed the error logging code. That and the aforementioned changes treating massless parts as having a minimum of 1kg of mass is really the best I can do. Bottom line is that if I don't have that PTD to work with then it's going to cause problems. And it didn't go missing because of a bug in Deadly Reentry. That happened somewhere in stock KSP where that data is generated.

- - - Updated - - -

Also, is there no way to just report a game bug, which is independent of OS and hardware?

[NathanKell]

I would call it pretty much working-as-designed, tbh: if you break physics, physics breaks you.

[Yemo]

I would call it pretty much working-as-designed, tbh: if you break physics, physics breaks you.

But if I set the physics significance flag, physics should ignore the part.

Also, massless parts are intended to work as an addendum to the host part, you could upgrade probe cores by attaching mass and physicsless parts, using KIS...