ScummVM sound is crackling - sound plays but it is not correct

I've installed Ubuntu Mate 20.04 (64-bit) on my Pi 4, and I then used "sudo apt install scummvm" to install ScummVM version 2.1.1

However, the sound on all the games I have tried is not correct at all, it just sounds like crackling static really (over headphones and HDMI).

Has anyone installed ScummVM and had success with it? I presume downloading and using the 32-bit OS instead won't make a difference?

YouTube works absolutely fine, the sound issue appears to be specific to ScummVM. I've tried using SDL_AUDIODRIVER to set Alsa and Pulse (after downloading PulseAudio) but the issue still remains.

I've been trying to change settings within ScummVM as well but I just get the same crackling.

Any ideas from anyone - I pretty much have just installed the OS and then tried to run this straight away, so I can't imagine other Pi users don't have this issue. I'll have to move back to Raspian if I don't get it sorted, that has ScummVM 2.0.0 working well at least. I've really liked Ubuntu Mate so far, so it would be a shame to have to bin it.

Edit: I'm going to try Bionic Beaver 32-bit to see if I have any more success with that.

SUCCESS! But I don't really know how. I was watching a video on YouTube and then tried again and the sound was resolved... I really don't understand, but it is working.