Whenever I try to level up a crusader, I keep on getting this: http://prntscr.com/8a631i
Doesn't matter which crusader it is, I keep on getting that, and no number of refreshes is helping.
It's weird because it was working fine until 2 days ago, and suddenly doesn't work now.
Did/does anyone else have this problem (and hopefully a solution)?

They are....
Is that a problem....?
I've gone over 5000 before without any problems, so why would that be a problem now?

Well, I hope it's not since I don't want to have my $50 turn out to be just a waste....

Well, after reading your reply, I went to the game to put in a help ticket and to see if maybe it happened to be fixed.
What I found is all of my crusaders were removed from the formation and reset to level 0 (level 1 in the case of the Bush Whacker).
Interesting thing is, even though they were removed from the formation, the border around the crusaders showed that they were still in the formation. Leveling them up even increased the displayed DPS. Might be another bug or two that has to be fixed?

Thankfully, leveling them up works for now, so I'll see if I can get them back up to 5000 levels again and see if I have problems again before putting in a help ticket.

Edit: Sadly, the error persists and I'm stuck again, so I've put in a support ticket.