Raw photos taken on my iphone copy to my macbook just fine, but will not now sync back to my iphone

I’ve spent some time looking into this and there are other reports of this. Here is the general consensus, it could be a software bug and an update will resolve issue. However, it’s also possible that Apple has implemented changes in this type of syncing and dng files are no longer permitted to sync this way.

If this is a critical part of your workflow I highly recommend PhotoSync. There is a fee or you can purchase outright. I used it for years and it’s excellent.

Your other option is to contact Apple Support and see if they are aware of any changes in syncing or iCloud sync.

Official Apple Support

Things may have changed, but the USB syncing model started back in the iPod days when iPods had very small storage capacities and very low-resolution screens, by today's standards.

Syncing full-size photos onto an iPod would have wasted a lot of space that could have been used for music, so when syncing FROM a computer TO an iPod, iTunes would often downsize photos. (It's not as if anybody would have the ability to see the quality loss when the screen was the limiting factor.)

Only when moving pictures FROM a digital camera TO an iPod and then TO a Mac using Camera Connection Kit accessories were full-size photos preserved.

I suspect that USB syncing in the computer-to-iPhone direction may, even to this day, still be downsizing photos and/or getting rid of things like Raw photos.

You’re not actually syncing them are you? You’re just copying them from one location/device to another, correct? If you are syncing, what app or service are you using?

What iPhone model and what iOS version are you using?

The Raw photos you refer to are in what format? Are they all produced by the Apple Camera app and are .DNG format?

iCloud backup and sync is off on both the Mac and iPhone?