I don't need a solution to this. I'm just here to let everyone know that there's a problem with timers.
It seems that if you perform an action at the precise time a timer ticks, it'll raise an error like the one below:
Int32 and CanAdd errors have also appeared.
Luckily, it isn't that big of a deal, but I've been able to isolate the trigger.
This particular error was caused by me trying to move to another room.
The CanAdd and Int32 errors might be different, but they seem to occur when I'm in combat and the game is subtracting from integers. I've only encountered these once or twice.