Crash when loading a mostly cleared map with party members

My regular party and I are all seeing a frequent crash to desktop, and have been for several weeks now.
The crash occurs when loading a map which the party has already mostly cleared (either entering late, or reentering due to death). It does not seem to occur if the map is recently loaded, only if progress has been made.
Attempting to restart the client and try again consistently results in another crash, unless we're no longer in a party together. Reentering the map works fine if the joining player has left the party.

My cache & crash dumps are at https://easyupload.io/yet8i5

Party member here.

To further elaborate on:

"

Reentering the map works fine if the joining player has left the party.

We see this crash instead when we see each other on the map as different parties. So instead of crashing on join, we crash when we get close to each other.

This error is very repeatable, so if there is any tests that people want, just let us know.

We have also been through all the best practice stuff like clearing the cache and turning off special effects.