Remove from SharePoint list with unique permisison not working

[Gianluca]

Hi there

I have a SharePoint list (with broken inheritance) and I add items (reservations) from a PowerApp. There's a Flow notifying the recipient of the reservation. In the same Flow I use "Grant access to an item or a folder" in case the the recipient of the reservation and the creator are not the same (for "on behalf" reservations). For these reservations the recipient is not able to delete the item (only the creator can), even if the recipient is listed with "Edit" rights in item details.
Any idea?
(Not sure if this is a PA or Flow question.)
Thanks!

G.