B9 Precoolers fix
Trying to attach a sabre intake to a precooler when using B9 causes an endless stream of null reference expeditions and stack overflows, causing many issues in the SPH (Parts not attaching; parts getting stuck to mouse cursors; unable to leave SPH either via exit or launch buttons or the menu; eventual lockup; other major glitches). Note that this is with other mods installed, I suspect that there is some KSP Interstellar shenanigans involved with the precoolers in some way.
These issues where fixed by removing/commenting out b9 sabre precoolers and intakes. I have commented out the sabre precoolers and intakes.
Sorry for not reacting to this earlier - I've been kinda busy.
Just commenting out the parts is not really conducive to fixing the problem. I notice your patch came after Chain Scaling was added to TweakScale, and there is a a bug in Chain Scaling that causes NullReferenceExceptions to be thrown, so I'm guessing that's what you've experienced.
Would you mind re-testing once 1.49 is released?