I have this function in my personal addon which worked until before Legion but it seems that Blizz changed something. Since the error message is kind of generic a search turned up nothing. I'm not really a coder, I just fumble around, so if someone could help me out ...
local function Hide(f)
Also I have some key bindings defined and I'm too stupid to find out which is the key binding name for lfg groups.
This one just works for manually created groups: