Syncing photos with IOS devices replaces all photos not just new ones

My "main" photo libraries or on my MacBook Pro. I sync specific libraries with my IOS devices (iPhone, iPad). As pics are taken with various IOS devices, I import them to the Photo library on my MacBook, then re-sync the library with my IOS devices. In the past, this has worked great and only the new/deleted photos were synced. Now, iTunes doesn't seem to remember the selected Photo albums for each IOS device from one sync session to the next, and instead, removes the photos from the IOS device and replaces the entire library. The net result is the same, but it seems to be to be an awful way to update photos on my IOS device.

Oh, and keeping with a related post, the sync does not maintain the album grouping - photos are synced, but not within the album folder. I have noted that, eventually, the album does appear, but it's days later. Weird.

I first noticed this issue after moving my photos from an old Mac Mini to a new MacBook Pro. I somehow think that's probably related, but not sure how.

Any ideas on how to fix this?

Thanks,

Bob