router – connecting with external ip is extremely slow

To be clear, I am an extreme noob when it comes to networking, so please be kind.

It takes an exorbitant amount of time to connect to my server (running on my home network) with an external ip (domain or the resolved ip), but only for certain ports. For example, when I try to load my webpage, it’s fast as can be, but when I try to connect to a cpu(1) server with drawterm, it takes several minutes. But then when that cpu(1) server finishes, and it needs to connect to the auth server, it’s fast once again. If I use the internal ips (192.168.22.*), these are all fast. To be clear, all of these use TCP.

My server is running 9front, but this is not a 9front issue, as I had similar problems when I was using void linux running some server software I wrote myself.

Has anyone experienced this before? Is it an issue with my router or my computer maybe?

Thank you in advance