The seasonal task information is a bit wrong.
That task says you need to complete Gulu normal 3 times for completion, but this is wrong.
A friend and I did GN together 3 times and did not get credit for the task. however, later on he completed the task alone.
I will try to figure this out later and will edit when needed, just wanted to see if anyone else had this problem.
A few tries later still no success and i am not the only one. Seems like some people are finishing this task without a problem, some even saying that they finished this in one attempt. I have done GN like 10-15 times now, each different scenarios. like killing leonardo last, killing barok last, and so on. i cleared my cache and junk and tried again with no avail. if anyone has info on this please let me/other know by posting here please. <3
Tested JohnBeck's fix, did not work for me; Doesn't mean it may not work for others. worth a try.