Loading websites takes a long time

[Lochkartenknipser]

Hello everyone,
I have a question about the Squid proxy. OPNsense version 25.1.5_5 on a Protectli VP2420.
I'm running the Squid proxy in transparent mode with C-ICAP and ClamAV. The UT1 blocklist is also active.
Everything's working fine so far. However, I'm having the problem that some websites take up to 5 minutes to open.
This includes the OPNsense forum website, for example. I then get a message at the bottom of the web browser, e.g., "Look up use.fontawesome.com."
If I reload the website several times, it opens.
Is this a setting issue in Squid?

Thank you very much
Markus