Instances won't stop crashing ("An unexpected error has occurred")

Every time I open up a map or go to a side area (including delve), there's a very high chance for my instance to crash.

Everything was running fine until around an hour ago, and then suddenly all my Hillock (Intervention) ambushes were crashing me 1-3 seconds into the encounter. The same seems to happen every now and then in maps without Betrayal encounters and in side areas, most notably in Delve. Ran into the same issue in lab as well.

I did try restarting the client for a possible hotfix, but to no avail.

Same, from the very leaguestart.

Entering instances leads to dc quite often
Hideouts, towns, acts, maps, delve - no matter. DC or 'account must be logged in' error.

Very big issue.