Screenshots duplicating in camera roll

Right my first post, so be gentle, i've read through some of these and they can be brutal :-)

I have iPhone X, on 11.4 iOS. My question is - does anyone know why my device would be creating duplicate copies of screen shots, so not all phones purely screenshots, the earliest one i have is from 31st May, since i noticed i haven't deleted any. I have noticed a few strange things so i'll try and bullet them here -

• Timing - the copy seems to be as if in batch jobs different times from the originals all copied at the same time, some examples
• 13/06 original 20:15 and another at 21:17, both duplicated at 21:17
• 15/06 originals at 14:15, 14:30 and 16:05, all duplicated at 16:14 - included a screenshot, different in sequence filenames and more or less the same file size
• iCloud - i read a few posts and duplicated images seem to talk about iCloud and Photo streams, so from way before this issue.
  • iCloud Photo Library has been off, i use my Apple ID on both work and business devices so i didn't want any personal stuff in the cloud,
  • My Photo Stream, it's been off way before this year.
  • iCloud Photo Sharing - Was toggled to On, however i've never knowingly shared or created an album, this i turn off a few weeks ago and the issue occured before and after, no change
• Today is the first conclusive example, original 08:13 i was at work, copy 12:51, i was still at work. My device was connected to Vodafone 4G but no wifi networks and all my mac's were at home (macbook pro and mac mini) my phone does not ever get connected to work PC. So this rules out any iTunes sync issues?
• I have two screenshot folders in Photos on my iPhone X, one at the top before My Albums, this has 197 images and dates back a while, the second is towards the bottom of My Albums and has 55 images, the oldest being 31/5, the same date i stopped deleting any duplicates, however i don't believe iu did anything to create this My Album. When i try and delete an image it offers Remove from Album or delete. Looking at the last image its the 12:51 mentioned above, so it's the copy, but i thought the principle of My Albums was they were actually more like filters, almost a metadata think so the Album name is the tag, you file images in this tag and can view them in one place, but the image isn't actually stored in a physical album, delete the entry in camera roll for example, the 'copy' in My Album goes too, so on this logic the mysterious My Album called Screenshots is fair enough (sort of) but why two images in camera roill and why such a random amount of time later?

It's not a massive pain, but it's unexplained and i don't like unexplained. Has anyone seen or heard of anything similar? Thanks in advance, Paul