I had meetme2therivers templates installed and I had a megahood using those. For some reason, my Sims 2 UC uninstalled itself so I re-downloaded and all my neighbourhoods and downloads were still there. So after starting up the game, some sims were glitching like they would just stand in the same spot and glitch different directions? Error messages would keep coming up about them like cancel/reset/delete. Even if I pressed reset, the error message kept coming up. It only affected some sims in a household and I'm not really sure how to fix this?

What exactly was the error message?

Error message only appears when I type in 'boolprop testingcheatsenabled true' to reset the sims. It comes up saying "An error occurred in object "N001_User(sim name and number) #450, Error: Undefined Transition."

That means that something your sim is trying to do is conflicting with something else on the lot. Something may have gone wrong when you redownloaded and things restored themselves. I wouldn't trust the version the game restored -- I'd revert to backup. (You do back up your game frequently, right?)

If that doesn't work, I'd start with the old standbys. Back up your game and work your way through the Game Help -- really do everything, don't just read it. Post what you tried and what results you got here if it's not fixed by the time you finish that.

I worked out that the problem was that I had changed inteen load order so I swapped that back and it mostly works fine now but my sims can't get pregnant for some reason and when they woohoo they're is a similar error message. I ran HCDU and it said inteen_b package was conflicting with all of the flavourpaks, is this normal?

I can't help you there -- I don't use InTeen. Perhaps someone else can provide more guidance?

As the flavour packs for Inteen are for the most part modifications of the basic settings of the mod, yes, conflicts are normal.

Which InTeen are you using, it sounds like you have the wrong InTeen. Either the wrong InTeen or a mod that is conflicting with InTeen.

I used to have InTeen (Flavour Pack) before and it did conflict with something, I think it was ACR. I got mad and took out InTeen