And no, it’s not the “memory almost full” notifier appearing but memory is actually available - that issue is known, documented, and a fix is out.
Here’s my issue: My wife’s phone is her camera. Her windows laptop however, is wholly incapable of handling the resource hungry iTunes. Syncing photos proved impossible. So I would plug the phone into the laptop via the provided data cable - and manually remove the photos by accessing the phone as a removable storage device. Just drag and drop into the appropriate file directory on our windows laptop. I then deleted the photos from the phone by highlighting them and clicking “delete”.
Each time we did this, unbeknownst to me, the amount of available memory on the phone was decreasing. It is almost as if the phone would not recognize that the memory was now “clear” after I removed the photos. The photos are in fact gone, and windows shows absolutely zero accessible files on the phone. However, the phone’s internal memory tracker shows no available space. When the individual categories are added up, the total is around 124MB. The phone has a capacity of around 6.3GB. It says there are 0 bytes available. Bad maths…there is nothing listed in an “other” category - there is no “other” category.
As best I can tell iOS does not have a Trash Can like Mac OS does (Recycle Bin on Win7), but that’s how your description sounds - the files are being moved into the trash can instead of fully deleted. I suspect this is a side-effect of the way you’re deleting them - maybe Windows is moving it into a recoverable place, as it just thinks it’s just part of its file system. Did you try emptying the Recycle Bin on her laptop?
The laptop’s recycle bin is empty. Always has been. I never drag/dropped to it. I just pressed the delete key on the keyboard. Since there were around 400 photos highlighted at the time, the recycle bin step was skipped, and the items were simply deleted. Took almost 2 minutes.
This user also seems to have had a similar problem, attempted to do a factory reset but did not see any results either, and solved the problem by doing a sync.