I can confirm crackling and audio artifacts with increased deterioration as time progresses on 5th gen iPad Mini with iOS 14.6 and iPhone Xs on iOS 14.6. Happens in both Safari and Chrome browsers. The way it progresses seems like a full buffer or memory leak, something that is increasing processing load beyond capacity. Does not appear to happen on 2nd gen iPad Mini on iOS 12.5.3 which runs the site very nicely, ran full 10 minute demo program without issue.
Thanks for dreaming this up! Haven’t driven any of my boxes with it but looking forward to rigging up and trying it out!