I think I may have the reason my decryption failed.
I noticed a (Key file-change)date discrepancy between the original file I encrypted and the last files I encrypted. Although I only ever created one key, several months after the creation, I signed the key.
The original file was encrypted with the unsigned key and I'm trying to decrypt it with a signed key
Thanks for your help, using the gpg -K, gave me the clue. (assuming I'm correct)