Users getting "wrong credentials" on login — likely server cache + nonce issue

Hi everyone, hitting a login issue on my FluentCommunity site and looking for confirmation from anyone who's seen this before.

Symptom: users enter correct credentials but get "wrong credentials" error. Not a redirect loop, not a spinner — a clear error from the form. Affects everyone (paying members, admins, new accounts), happens both in browser and PWA.

Setup:

• WordPress + FluentCommunity (login at /?fcom_action=auth)
• Hosted on Rocket.net (server-side cache active)
• Cloudflare DNS-only, not proxied
• No caching plugin

My theory: the FluentCommunity login form is protected by a WP nonce (24h lifetime). I think the server cache is serving a stale version of the /?fcom_action=auth page with an expired nonce. WordPress rejects the POST, and FluentCommunity returns a generic "wrong credentials" error (doesn't expose nonce failures for security).

Evidence:

• Worked fine for several days, then suddenly broke
• Disabling/reconnecting plugins temporarily fixes it (probably purges some cache as a side effect)
• Matches the "Nonce has been renewed" pattern reported in other Fluent threads

Questions:

1. Has anyone hit this exact "wrong credentials" issue with FluentCommunity?
2. Is there a known list of URL patterns / nonce names to exclude from server cache for FC to work properly?
3. Does FC expose the underlying error somewhere (logs, hooks) so I can confirm it's a nonce failure?
4. Any way to refresh the nonce via JS before submission, or extend its lifetime for auth?

Already opened a ticket with my host to exclude /?fcom_action=* from cache. If anyone has been here before, I'd love to skip ahead to the solution.

Thanks!