The white swet causes a forloop to happen, and you are removing effects while it is parsing through the different effect.

to fix:

Create an empty ArrayList and add all of the player’s status effects. then parse through this new arraylist and remove player effects accordingly. Hopes this helps.

I took a peek at the code, and I don't believe this is the case. I'll look into it later when I'm at my computer though

Looking at it as well, I agree with @Jack-Papel and I havent seen any such issue.

Furthermore, this was the result, when I formatted PR #267

The result is identical, but with a bit more overhead shoving everything into a new list...

After some review and testing, it seems that this is indeed an issue in some circumstances.