Just an update on this. Turns out its not so much of a tragedy after all. Now indeed the material is on 24, and the sound stamped at 24 syncs fine apparently. The files that were recorded at 25 were drifting but restamping with waveagent did the trick. haven't heard back for any problems so far and hopefully no drifting due to the camera, but I still don't know the exact model it was.
there will definitely be an issue with the camera noise messing up the dialogue (for CUs at least), for which we did wildtracks and recoded the rehearsals, but I imagine it will still be a pain. ADR is not an option, perhaps denoising will
Are there any strategies for this problem at filming stage? kinda off topic now i guess