I have read here that you can downgrade to a previous /e/OS version by flashing its ZIP in recovery mode. This is more or less what I did, but together with a factory reset, so it wasn’t a real “dirty flash”.
Still, you should definitely make a backup beforehand of all your data… and be aware that you still do it at your own risk.
EDIT: Maybe another user has more experience with downgrades/rollbacks? You may also search the forum (or the internet) and see whether you find more information about rollbacks.