I think the problem is partly down to browser and cookies caches on people's machines.
Try and clear those and it should help.
I'm hoping to reduce our current 2 yabbfile folders to just one where it used to be.
As well as reduce the templates folders from the current 3 to the expected 2.
Which will either fix some things or break some other things.
There is still some weirdness going on that i hope to fix.
I need enough time to sit down and have a proper session on it (and maybe even read the manual).
But it is interesting that it's working with chrome though.
Possibly java updates are needed ?
(don't know if yabb uses java - but that might be one explanation)
I just need the time and inclination to coincide on the same day