People are focusing on your very non-standard setup, but I've experienced this - less than you to be sure - on a standard MacOS setup with Firefox and only uBlock Origin installed. If I switched to Chrome without uBlock Origin it worked. This was on the English National Ballet's ticketing website.
Same problems here. Mac OS with firefox + ublock origin (and a dns based ad blocker) jams me up. Switching to Safari (with dns ad blocker still on) makes it work
Has become increasingly more common in the past few months across several sites.
