if you can reproduce your lowest roll +3 you can add this information here with the player log and steps to reproduce.
you don’t need to test with rarer Affixes, that shouldn’t have an impact.
what you can try: collect magic and rare gilded crowns, remove the affixes with rune of removal or rune of cleansing so you start on an empty gilded crown with already some instability. i made two FC yesterday this way and they rolled randomly as expected.