Its not every time, and i only just caught it but now that i have seen it for sure, the other 3 times i thought it happened it def did.
So im currently doing quick reset runs for div gems.
during those i also like to use the quikc refreshes on the shop to get some of the harder to get items and enhance them.
but several times now the enhancement just vanished after resetting.
im not sure how exactly this is triggered but ill keep a look out for it.
from what i could tell the items it happened on were the Rigged dice, and the ungodly flail.
when going from great to epic.
i mainly just enhanced them, often times just buying the enhancement thing from the forge for it, then doing nothing else with the items and hitting hard reset.
maybe not doing anything with the items causes it not to update, or not update fast enough until i reset? no clue.
ill try to see if i can extract a save file so i can retry this much faster/often