It's an issue with the board. IPB staff is working on it.
I'll try to manually unarchive them now, but in the past it has destroyed some active threads so have been hesitant to do this manually until a fix has been tested. That's what happened to the CVPS / SolusVM exploit thread though I think we're close to having that fixed.
Sorry about this, I know it's an inconvenience. Some great tutorials in there.
I had enabled an 'archiving' feature, however did so with non-optimal settings/rules in place for it. This resulted in many topics being archived in the background for hours before I noticed. I set the rules differently and tried to UNarchive any post that has seen activity in the last 365 days (so that would be every topic) however it broke. It didn't UNarchive everything and some of the things it did UNarchive broke the threads. One thread was 30+ pages long and dropped to 13, we're trying to restore it now. Was just informed of a ticket update where they said they were going to try something different, they did it locally and they got the 1,000+ posts imported properly so going to try it live soon.
After that, we'll address the issues with the other posts.