Edit: The issue I describe below was most likely caused by me having a Retro Replay cartridge inserted while playing the game. Gregor told me that he recommends against this. Removing the cart and replaying the game I managed to finish it without the game freezing up when saving. Thank you to Gregor for his incredibly quick and helpful support. Rating changed to 5 stars.
Original Post:
While I have enjoyed playing this game as much, if not more than, the previous two, I have twice experienced a game breaking bug that prevented me from completing the game. The bug occurs when using the save game feature late in the game, after I have collected all three artefacts and am moving towards the final showdown. Pressing F5, the disk activity starts and after a few seconds the disk head movement stops, BUT the disk keeps spinning and never stops. The game just keeps displaying "Saving" I have to restart my C64 and the game to resume and then pressing L to load the saved game from the title screen menu ends abruptly as the saved game has been corrupted. Incredibly frustrating as I had fully mapped the game and very much wanted to see the ending.
As it is I really can't recommend the game as it is brutally difficult to complete without saves due to the mostly random nature of combat.
I should note that I'm playing this on an Ultimate64 with the latest firmware.