If you think it is a bug have you reported it? https://forums.dovetailgames.com/threads/how-to-contact-our-support-team.3000/
It's not really a bug per se. The default version of TS is 32-bit, the 64-bit version is basically an add-on/update. You have to Choose the 64-bit version when you start TS - if you didn't choose the version TS would automatically start in 32-bit mode. So when TS restarts after a cache clearance it starts in default 32-bit mode. It is certainly worth asking DTG if it can be changed, or create a .bat file that clears the cache outside of TS. Similar to this: SET RW="YourinstallationPath"\STEAM\SteamApps\common\railworks\Assets DEL /S %RW%\Blueprints.pak*
My "Clear Blueprints" bat file sits in the Assets Folder and I have a Desktop shortcut "del /s *.pak pause"
P749 Do you use these other options too? del /s *.tgt del /s *.cost del /s *.bak* del /s *.xml del /s *.pak
pH, I don't bother with the others. *.bak files are created by TS Tools when modifying assets If I deleted them the opportunity to revert would be lost