this happened in the random upgrade challenge on the bridge level, I died but had a clone, then immediatly after I died, (before I respawned) the last guy died, then it crashed as I entered the elevator
We're preparing to address possible causes of this bug. The reports so far are pretty consistent as far as when it happens, and I have been able to cause it during testing at least once, but otherwise it has remained elusive for me.
With so little console information to go off of from the console output, there may be more to a fix than is typical, with a lot of exploration, or possibly coming up with a sure-fire way of reproducing it.
It's not great but it seems rare. You should be able to play normally if you restart, but let me know if this is not the case and I will work with you to fix the issue. :-)