I was having a similar issue but only android phones?
only first-time visitors were having an issue, If they refresh the page then they could enter it? I didn’t want to roll back plugin because updating it fixed other issues. So found that I was Cashing the checkout page through Cloudflare- I made a rule not to cache checkout page it seems to have fixed it..
Not sure if regular cache plugin would cause the same issue.
Hope this may help someone with the same issue
Regards
J