I removed the prefs.js and restarted zotero, it still gets stuck at loading items, also showing message box "Better Bibtex: Initializing \\ Waiting for Zotero database". Is there other approach to fix this issue? Such breakdown always happen just before a deadline, it is driving me insane.

I'd be glad to help, but I do indeed need an issue to be opened on github.

No worries. I solved the problem by replacing zotero.sqlite by its backup zotero.sqlite.bak (and of course rename it). Changes to zotero in the last two days were lost, but it is better than a ruined lib.