(I'm mentionning this issue : #990 because I think It's linked with the correction made during this ticket)
We tried to make a Laviathan come in the overworld to make a "museum" of mobs, it worked for a while, but then a friend came back to the nether, then it made many Laviathans spawn to the place the carver portal was, now each time we load the chunk containing those, the server becomes very laggy until it crashes
Here is the crash log :
crash-2022-03-22_21.01.50-server.txt

Now I'm kinda stuck because :

• If I try to kill the Laviathans with the chunk not loaded, it doesn't work because no entity found, which is pretty normal to me
• If I try to go to the chunk to load it, the kill command isn't accepted by the server because he's crashing because of the Laviathans
  I'm using this command btw : /kill @e[type=alexsmobs:laviathan]
  And the server is on 1.18.1, mod version 1.17.2
  Thanks in advance ! :)

Same happening to me, exact same issue