Ritual altar cannot be clicked in grave trough

Bug Report ID: #4241293627

There's always one altar that cannot be clicked no matter what, until the map boss is killed (even though the altar is in the middle of the map and not in boss room), i've done multiple grave trough maps and the bug always occurs. It appears as clickable on the map (gold/before fighting mobs) whether tabbed or not but there's no button to start the encounter, even if the top-right counter shows 1 monster remaining, which is the boss. Haven't tried other maps