This issue exists at least since GpgOL version 2.5.6-beta5 (but I guess since the start of this feature in 2020).

In the context menu of a mail in the message list there is an action "Permanently decrypt" at the very bottom.
If you click it after cancelling the decryption of the mail at the pinentry this results in a "decrypted" mail with the content "encryption not possible":

The original mail content is thus permanently lost.

This does not occur in other cases, that is with a not decrypted mail after pinentry timeout or after giving the wrong password. In this cases the function "Permanently decrypt" does nothing without emitting any message.