RAW images convert themselves to TIFF images within seconds of importing to iPhoto on MacBook Air M4

I am transferring RAW images from my Nikon to my MacBook Air M4 (and iPhone, but I get the same problem, so we'll stick to this being a MacBook Air M4 problem for now). In the first few seconds, there are no issues: I see the RAW images appear in my RAW folder on my MacBook, highlighting a successful transfer. However, after half a minute or so, slowly but surely a certain group of pics, 30 or so, start to delete themselves from the RAW folder in my photos and transfer themselves, without any of my doing, to my normal Photo Library. They have been converted from a RAW file to a TIFF file. This only happens to this particular group of photos; all other RAW images do not have this problem. All pictures are taken from the same camera and on the same SD Card, even the ones that do not have this problem.

Why is this happening? How can I stop this from happening?

TL;DR images convert themselves from RAW to TIFF files within seconds after being put on MacBook. Happens to only a select group of pics, all from the same camera. This doesn’t happen to all other pics from the same camera.