Minecraft 1.12.2
Botania 1.10-361
Extra Botany 1.1-55-fixed
Forge 14.23.5.2836

We set up a Gaia III fight with two players, one of who had a totem of undying (from vanilla minecraft) in the left hand (normally for shield). Fight started as expected, until the stage with the giant swords in the sky. One player died quickly (me), and was sent home. The other died about 15 seconds later, but according to the crash log, the code to trigger the totem of undying caused a server crash

Crash Report:
crash-2019-08-24_01.45.44-server.txt

Restarted server, second player attempted to log in, which caused an immediate crash because the Gaia III fight was confused by the lack of a player.

Crash Report:
crash-2019-08-24_01.49.34-server.txt

Restarted server one more time, had a player who hadn't been involved in the fight at all log in and go to the arena to make sure the fight was terminated, then others could start logging in again.