I had to cross brace the long mounting plate that is meant to bridge the hole & hang the fixture from. Like all electrical things it was too damn small and kept pushing up into the hole.
I had to find a tiny 1" screwdriver to fit up in there when replacing that thing.
Good grief 2 hours of contorted torture. Not to mention holding your arms & tools above your head the entire time. 🥵
But.... it f-ing WORKS NOW!!! Bam! 💡