Breaching the 2nd Cavern layer on Elevation -107 causes the game to suddenly lag moments after the breach. I do breach near a deep pit into the third layer. I can breach the third layer with no issues. I'm not sure if the deep pit maybe the issue. Using DFHack to "eliminate" all creatures doesn't resolve the lag. Only after "reveal" command is used does the lag disappear. The game does run slower than pre-breach, probably because it's now rendering the entire map, but it's acceptable.

Attempting to undo the now revealed map causes the lag to return. I do not believe it is caused by the need to harvest cave spider silk. There are two forgotten Beasts on the map. One is in the first layer, the second only appears after the second cavern is breached and the "reveal" command is used. I do not believe these are issues neither.


Steps:

1) Dig/Stair out the North and North-West blocks on the stairway in Elevation -107

2) Let the game run for a few seconds to experience the lag


Additional Info:

Version 50.14 - Steam
No mods
DFHack used after the lag was discovered