Well that maybe helps narrow things a little… perhaps!
Let’s try this: forum admin > toolbox > housekeeping – and run the task ‘reset auths cache’…
The code makes jus two checks.
And that’s it. So we checked the first condition yesterday and we have checked the second one today. And I am assuming here that you ARE logged in as a fully fledged forum Admin.
After that we would be looking at code errors… but we have checked for those as well. So I am somewhat puzzled…
If you open your own profile form – permissions tab and view a forum can we safely see that Upload Avatars IS ticked on (in the uploads section)?
Hang on…
Has this EVER worked? And by that I mean you NOT allowing your users to upload avatars and you doing it for them?
Yes!
My permissions are fine and I have always uploaded avatars for the users.
I have never allowed them to do it. When I need to, I switch on the function and upload the images myself.
But now it’s not working any longer…
That’s actually just more puzzling as I think I have found the issue but if I am right it never should have worked!
The problem, I believe, is that when that test is made as I described above – test 2 for the user is being made against the user ID being edited and NOT the user making the edit. Thus you can’t upload for another user who does not have upload permission.
So weird why you should have ever been able to do this. But… I will dig deeper and we will get a fix out as soon as we can.
its a fundamental shift to how profiles work… and was blocked by design… if users dont have permission for something, why would admins be able to set? likely wouldnt work on front end anyways…
but we are talking about making a special case for uploaded avatars…
SOLVED! 
I have no idea why, but I fixed it. I just checked the permissions and the members weren’t allowed to load avatars.
I changed that and now I can load them.
In admin–>profiles–>avatars, I can prevent them from loading avatars.
The strange thing is, it has always been like this. Now it’s different…
But it works!
Thank you for your help! 
yes, that is what Andy and I were saying… and talking about a special use case…
thanks for the update!