Well, I don't think it's the root cause of your problem, but you do have an odd issue with your DNS. See the DNSViz report:
https://dnsviz.net/d/_acme-challenge.eptest-1.test-001.xcu2-8y8x.dev.cldr.work/dnssec/
_acme-challenge.eptest-1.test-001.xcu2-8y8x.dev.cldr.work/TXT: A query for _acme-challenge.eptest-1.test-001.xcu2-8y8x.dev.cldr.work results in a NOERROR response, while a query for its ancestor, xcu2-8y8x.dev.cldr.work, returns a name error (NXDOMAIN), which indicates that subdomains of xcu2-8y8x.dev.cldr.work, including _acme-challenge.eptest-1.test-001.xcu2-8y8x.dev.cldr.work, don't exist.
That is, the NXDOMAIN response is supposed to mean that there aren't any responses available at all for any subdomains of it either, but your system is responding to xcu2-8y8x.dev.cldr.work with NXDOMAIN even though subdomains are giving other responses.
But again, I don't really think that's causing the problem you're seeing.
Aren't those supposed to be POST-as-GET requests anyway? I think the latest update still had them enforcing that in staging even though production doesn't.