Credit to Lyranica for figuring this one out.
Platform, device and operation system
Android 11, Samsung Galaxy Note 20 Ultra
What were you expecting to happen, and what actually happened
Expected: Play a full match of Co-Op in a dungeon.
Actual: When a player is still on an altar selection screen when the co-op dungeon run ends, the dungeon run crashes.
This is a bit of a unique problem that is in the limelight because of the implementation of “Easy” mode for dungeons. Level 50s running around in very low level dungeons chasing spell drops can cause all sorts of havok when they progress through the dungeon too quickly.
This issue tends to manifest around the 2nd altar choice, late in the dungeon, when large groups are in play. Fast players can end up completing a dungeon while party members are still deciding their choice on the 2nd altar. If any party member is on the altar selection screen when the run ends, the run crashes (the game does not know what to do with the player on the altar selection screen).
Being on the altar selection screen:
Ending the run with another party member still on the altar selection screen:
How often does this happen? When did it begin happening?
Always, we think, given this chain of events?
Steps to make it happen again
Play a low-level dungeon with high-level characters (for best results use a full party).
Advance through the dungeon normally.
Leave one player on the 2nd altar selection screen without making a choice for that player.
The remaining players clear the dungeon, as normal.
The run should crash when the dungeon attempts to close if there is a player still on the 2nd altar selection screen at the time the run ends (all opponents defeated).