Slow GUI on FQDN. Fast with direct IP

[Daves_nt_here]

Just added my LetsEncrypt cert. I access OPNsnese through the FQDN but most times it will take 1~2 minutes to load. When it does load, everything is fine for a min or two but then clicking on any option causes the 1~2 min delay again.
If I access it from the IP address https://192.168.5.1:8443 it loads as expected.
I tried adding an Unbound DNS host override: opnsense.domain.com > 192.168.5.1 but that doesn't seem to make any difference.

[meyergru]

It is unlikely that the DNS resolution takes that long, so DNS is probably not the problem here.

Toggle the "OCSP must staple" setting in the certificate. If the webserver does not support it properly, it could lead to slow download of certificate revocation lists, which in case of LetsEncrypt should be huge.

[Daves_nt_here]

That seemed to do the trick.
Thanks for the help!