Strongboxes in crypt map failing to spawn monsters and open

Report ID 3,132,557,536

Title sais it all.

Most likely failed to find a valid tile to generate monsters.

Note that the monster count is 0.

I also ran into this issue. but i had 2 strongboxes, the first strongbox spawned all their mobs. The Second one did not seem to finish spawning the mobs. I did start both of them at the same time and cleared the mobs from the first one.