iphoto sync issues from MacBook Pro + can't delete from phone

Good Morning and thanks for any help in advance.

hopefully this is a really silly issue and easy to fix but I cast get my head around it.

I'm one of those that like to keep a back up on my MacBook Pro and organise my photos on my MBP instead of on my iPhone. so doing my usual couple of monthly move photos from camera roll to certain albums on my MPB, I noticed that after it was all finished syncing I was missing about 3000 photos, Photo app on MPB has roughly 15000 photos and iPhone only had 12000, so though ok ill just delete all photos from phone and start again. for some reason I have 7500 photo in my "library" on my phone that can't be deleted, just no delete option when they are selected either individually or grouped, but when I look under the albums tab on iPhone I have nothing there. its almost like they are stuck and are affecting sync from the MPB but I can't get rid of them.

Running up to-date software on both MBP and iPhone 13 Pro Max and I'm just a little stumped.

and help will be greatly received.