I can't tell why joymax did that check, because I don't know what skill type with Param1 value 4 is, but I can tell how to fix it.
Basically, your skill with ID 33788 cause that because its Param1 value is 4 and its used on specific target. So, try to find out what Param1 value 4 means and remove that skill until you find out or change Param1 value to anything else than 4.
