Let’s start at the beginning. Is this a recent upgrade? And are you able and willing to take a quick look at your database tables?

Yes, it’s a new upgrade. Here’s some background.

The site and forum were instituted quite some time ago. Just recently we have gone through a revamp, and in the process noticed that the Simple:Press installation that we were using (4.1-something) wasn’t working correctly — so we downloaded the new version and upgraded without any obvious hitches — at first. All forums, posts, and members carried over just fine. Once we got deeper into the setup, though, we realized the above problems. 

I’m willing to strip it down to the bare PHP, if that’s what it takes. Where exactly should I be looking?

We had a small handful of users – about one a week or one every two weeks – for whom the permissions got screwed up somehow. We have never been able to replicate it even when a user gave us a backup of their pre-upgraded database and let us try! For us it just upgraded fine. For him it screwed them up. We have spent hours trying to find the glitch and afraid we never have.

I suspect this has happened to you. And I am really sorry to hear that.

There are basically two ways to fix this up – assuming this is the problem – and it does sound like it hence my first question.

The first is to literally work through the database tables removing duplicate records which mainly seems to be the result of the problem.

But – if your permissions are fairly straightforward and you haven’t done a lot of customisation to them then going to the forum admin > Permissions menu and choosing ‘reset permissions’ will clean them all up and put them back to their default settings as delivered on a new install.

Then you would need to just check through them all and check each forum had the correct pairing of permissions and user groups.

So would the second one cause too much pain?

Wow. I’ve done the latter, and provisionally it seems to have worked. I’ll hold off declaring complete success until I’ve done more testing, but now everything that should be visible seems to be.

True, it will be a nuisance to go back and reset all of these permissions, but a little mindless busywork is an acceptable trade-off to get things working. 

Thank you a bunch for your help. I’ll let you know if the issues continue in some way.

Good news and again apologies. I really do wish we could find the culprit… that one combination of data and events that causes this.