Reaper distorts all VST synth sound output (M1 Mac)

[dottjt]

I recently bought a new M1 Mac mini and I thought I'd also buy a Reaper licence as well, since I loved using it on my prior MacBook laptop during the trial.

All VSTs run inside Reaper are distorted (like a really fast LFO has been passed through it). I've tried Vital, Surge, ReaSynth and Helm and they are all completely distorted.

What's interesting to note is that these synths when run stand alone on the Mac, sound perfectly fine - so I assume there's a bug with Reaper.

I've tried using both the Intel and ARM variants of Reaper, and both produce the same issue.

It sucks because I spent money on it, but also I guess it's my fault for going ahead without checking compatibility first.

Anyone else have this issue?

EDIT: I am also on 11.2.1 Big Sur with version 6.23 of Reaper.