Transparent SSL-Proxy not working correctly when using RBL

[WIT-Jansen]

Good Morning,

I have a specific problem with the web proxy on a currently running virtual OPNsense 22.7.6-amd64.

We are using the transparent ssl-proxy setup based on the guidelines of the documentation.
SSL-Bumps are all set, in general the setup is working but as soon as I activate the (we are using the UT1) RBL, some HTTPS-websites don't work anymore.
A few important ones for example banking sites can't be openend and even if I choose for example only the category "Manga" to block, these banking sites won't work anymore.

In the RBL-option I tried it with and without the button "ssl ignore cert" but nothing changes.
I also checked the content of the manga-category and searched the files for the specific problematic Domains and URLs but nothing there.
And I also put the domains on the whitelist with the simple and regular expression variants, nothing changes.
As soon as I deactivate the RBl again, everything is working fine but of course then the webproxy is useless for us.

In certain cases I get the HTTPs errors and in others I get an access denied via the OPNs but again those Domains/IPs are not present in the RBL-Files.
I also set the "alternate" DNS-Servers, so the OPNs uses the same ones as the server who wants to reach those websites.
Does anybody have a clue, what it could be?

Thanks in advance for any possible information or help to this case.