Yes. The issue comes about from the cursing logic being too basic in OldRoutine and not handling the case of the delay between when the bot curses the mob, and when the mob actually gets cursed on the server. As a result, it executes the logic twice, which is faster than the server told the client the mob is now cursed.
A better routine in the future would avoid this issue but for now OldRoutine is stuck as-is.