Good luck everyone! The sprint will be on come Feb 21.
I actually found 21 names somehow!

Took me a while to figure out which one wasn't counted.
~
That's great news,and thanks for the tip plen, so now I have to find actually 5 not 4 names. It's gonna be fun to figure out which one is not included. Now I saw that the time of the locked transaction is actually Sun Feb 21 2021 00:00:14 EST, that means 05.00.14 UTC, I guess I won't be the first in that challenge but I'll try my best.
Good luck everyone and thanks for the tip again.
Oh I don't want to lead you on a wild goose chase. The member in question that I had to remove hadn't posted since 2015. I spotted a common word, did a member search and thought I had verified that they were active. Only after trying many things with me thinking I had the 20 usernames did I figure I got one wrong. So I revisited the list and spotted the error and had to thus go find the real 20th user.