iPhone only syncing 'some' iCloud photos

Hi everyone,

Hope you can help.

Recently I've used my Macbook Pro and the Photos App, to deleted photos from inside hundreds of smart albums, so that the photos are now in my recently deleted folder and the folders are now empty...

...these changes are replicated directly in iCloud through browser, which shows my Macbook's Photos App is syncing correctly with my cloud storage.

[ I do not use photo stream and never have, it is not turned on and the photos I'm trying to organise are older than 30 days anyway].

The problem I'm having is that although Photos are syncing between my Macbook and the iCloud, this only appears to be 'half' the truth for my iPhone.

Some of the changes (clearing entire folders of photos) have only affected a small number of the folders on iPhone, not all of them. For example. My Whatsapp folder (cleared all contents entirely) is completely full, yet some folders have been emptied (which I'd have expected if syncing correctly), but then other folders seem to have only removed half the photos that were previously there, there not consistency.

I've left my phone on all night, in case my iPhone is just being slow and needs to catch up, and sure enough some folders (the ones that did appear to sync properly with my iCloud changes) have disappeared from sight, but something is definitely not right, as looking on iCloud I've hundreds of photos in my recently deleted folder, and only about 50 in the same folder on iPhone.

Both iPhone 7 and Macbook pro 15" are both fully up to date.

[The folders disappearing from my iPhone overnight actually adds another layer to this query, since I never actually deleted the empty folders through my Macbook Pro, just their contents. The empty folders still appear on iCloud, so I've no idea where they've went from iPhone.]

I've tried turning iCloud photos on and off under settings, only thing I've not done is sign out and back in again.

Any ideas what could be going on? Thanks!