Basically when I export a PNG image sequence and open it in AE frames are missing. I do animation so that really messes things up.I've had this problem for ages but worked my way around by exporting files as mp4 from Photoshop before improting to AE. Now I'm on mac silicon and it's messed everything up as it only allows for renders of image sequences. At first I thought it was frame interpretation but I changed the settings so that all footage imports at 12fps and still AE eats up some frames.
Could it just be a previewing issue? AE sometimes skips frames to try and give the illusion it's capable of playing back in real time. Try rducing your work area so it's just around the few seconds in question, let it cache those frames once and then see if it's still skipping. Or if it's not too much trouble you can render out the sction an see if the frames are there.
Without exact info on the sequences, settings etc. and ideally screenshots we can't really tell you much. And well, that dreaded M1 in itself sets off all kinds of alerts, given how poor compatibility of Adobe software with these systems is at this point... It may just be a bug and you may need to use a different format liek TIFF or native PSDs.