I'm currently trying to edit a live event and sync up the two cameras so I can do a multi-cam edit, but one of them seems to gradually speed up slightly (like it shows 2 frames before the other one), like it's 24fps or something, but it Premiere says it 25fps. I know one is 50i though, the one that gets in front, would it being 50i cause it to not sync up?

I try and re-sync up, and it just eventually starts to slip out of sync, any ideas?

It's normal drift when there's no genlock, just work around it, re-sync when necessary, no big fuss.

Not sure if that is normal behavior for a video camera, I have been doing several multicam shoots over the past years with different brands of camera's mixed and never seen the footage slip out of sync (and I don't use genlock), also not with 25p and 50i mixed.

Well, in the past I've not noticed it when using two of the same cameras, but this event shoot didn't want the extra expense of hiring in cameras so I had to use what I own.

Do you ave any other NLE you could try importing those 2 deviating camera's and see if it's still off?

No unfortunately, I'm going to try re-ripping the footage with HDVSplit instead, see if that makes a difference.