I spent quite a while today debugging why even after a full reset of our project (we tried upgrading to 2019.3.0b6 with Accelerator but decided to go back to 0b3) it still froze on importing. Turns out, the preference to use Cache Server on v2 asset database is a shared preference between 0b6 and 0b3. So the 0b3 project now had the preference of "Cache Server: on" pointing to the Accelerator server. This resulted in a complete freeze on asset reimport, library deletion didn't bring anything, it would always get stuck at some point. Workaround was to create a new project on 0b3, disable the Cache Server completely again in Preferences and then launching the original 0b3 project. Voilá, reimporting just fine, processor is doing something, loading bar is progressing... That's a really weird side effect!