I am seeing the same behavior if I disable all addons, so this cannot be an issue with Premade Groups Filter.

Steps to reproduce: I logged into my toon, all addons disabled. I signed up for a group. At first, it shows only one green group listing. If I click the reload button, I suddenly see a duplicate of the group I just signed up.

Could you please check if you see duplicates if you disable all addons?

Also see #65

I just found the bug on Stanzilla/WoWUIBugs#224 and there are also posts in the US forums pointing out this issue. This is a Blizzard bug. There is also a small code snipped you can paste into any addon lua file to temporarily fix the problem.

Just at the end of any lua file of any addon, e.g. Main.lua of PGF.

Where exactly do we post this "small code snipped"?

Appreciate it. Hope it works.