Based on my testing, the bug is most likely triggered by one of at least 2 types of crash, which are most likely to be triggered by a 'quick' click to use a portal or exit. Pausing for 2-3 seconds before clicking does seem to greatly reduce the chances of a crash.

Why it gets stuck I'm not sure, it seems to be restricted to the online game only, therefore connection and the online server are most likely where the problem lies. My guess is that it's a server bug.

Working around this on the online game is difficult, sometimes it's because the crash (and/or *something* happening later) causes a duplication bug, only finding/selling those duped items will 'fix' it.

Other 'causes' appear to be down to *some item(s)* in the Inventories of VH and/or Lady K. Selling the items that appear in the inventories at startup often fixes the 'bug', though often it's only temporary, as once a char is 'infected' (happens for new chars/accounts from lvl 4-14, in my testing), it usually happens again after 1-4 levels.

Transferring the 'bugged' dupes, or the 'bugged' Inv items, to another char seems to transfer the bug to the other char!

Yes, I've had chars that revert to lvl 1 as well; usually I create a new char and do 1-3 lvls in Adventure Mode, so before any restart those chars should be ~4-9.

Try logging out and spending a few hours in offline mode with some fresh chars, note down any diffences seen - there will be some, even disregarding any crash/reversions - check all onscreen details, NPC/Quest payouts, etc.