Hello, it should work perfectly in Amstrad models. In fact I have a Spectrum +2A to test the games. It sounds weird. The game uses all memory banks, please try to make a RAM test in your machine.
Update to say it was a RAM issue - even though all RAM tests passed, I swapped it all out and boom game works perfectly - and all the others that didn't work either. It's a brilliant game too, thanks very much!