If gelatin cleared it up that quickly, the haze was caused by yeast. Why a 1 micron filter didn't remove that like it should, I'm not sure. If anything a filter than fine would be prone to clogging. Are you sure it was assembled correctly?
Yes, assembly was correct. The beer went through a 3 micron filter first. I did make sure to connect the "in" line to the "out" line on the keg. When I pulled a sample, it was still cloudy / hazy. Then I figured the 1 micron will clean it up. Nope! Still hazy.
I started filtering at around 5 psi. Near the end, had to bump up the pressure to 10 psi.
The filters did not clog.
Yes, after adding gelatin, this beer is brilliant clear today. After less than 2 days total time.
What is odd is that in previous filtering with a 5 mic followed by a 3 mic, the beer was always brilliant.