@MaxwellsDemon that's an issue with ContractConfigurator which is a dependency of just about all contract packs and is somewhat unmaintained right now.
See the post below by phoenix2004uk for an mm patch then keep reading for methods to fix it in an existing save.
As for the PartSet bug, I get it, too. Don't believe it contributes to any crashes (ksp doesn't usually log anything useful in diagnosing a crash, therefore logspam can be annoying but might not be your most serious issue). Most likely memory access crashes. Uninstalling scatterer improved the frequency of these for me (makes sense as it is out of date and players have been reporting the same experience for years).
Other mods mentioned that can cause issues:
AmpYear and [X] Science! - both allocate a ton of memory every frame, AmpYear scales with part count, x science with experiments and situations.
Kopernicus (at least the 1.7.3 version) has problems with scatter, breaking ground features, and bodies with no oceans. There are workarounds available in the support forum for some of those issues.
