That’s annoying, unnecessary and pretty disruptive halfway thru a project.
But at least you’ll only have to deal with this awkward reconform once or twice - after which everything will be at true 24.
So in Pro Tools, you’ll probably want to start using the pull up/down feature in session setup - and if it were me, I’d be pulling the video speed rather than messing with audio.
The good news as far as Matchbox is concerned is that 23.98 and 24 ARE the same thing when it comes to reconforming. Matchbox just sends timecodes to Pro Tools, so it doesn’t care how fast you are running those frames past the audience.
The sticky part will be getting the 2 movie files to 23.98- There used to be a thing from apple called Cinema Tools which could do this just by tweaking the header. What you absolutely must avoid is something like Quicktime which will invent new frames or delete frames and completely mess up your sync.
Also - if you’re importing AAFs from your editor, these will be marked with the framerate of the project - so if these are now showing 24 instead of 23.98, Matchbox will refuse to import them. EDLs won’t have this issue as they don’t carry any framerate info at all (wtaf?).
We do have half a plan to allow importing movies like this and have Matchbox “pull” the framerate - but it’s a bit of a strange thing to support. In any situation where it’s necessary, you probably have something very wrong happening somewhere up the chain - and you really ought to address that thing rather than hack past the issue.
Hope that’s helpful.
Stay safe out there and don’t mix framerates kids.