Pakfire proxy connection broken

For testing purposes i installed behind my main ipfire another one. Only proxy connection are on my main ipfire allowed. So on the test machine under web proxy i have the correct upstream proxy. My problem is pakfire give me only error. Behind the test machine, proxy connection from a client are also ok. Also ntp. Both have Core 141. It looks like

Wan <-- main ipfire (only proxy allowed) <-- test machine (pakfire broken)<-- client via proxy ok

pakfire: Giving up: There was no chance to get the file 2.25-x86_64/lists/server-list.db from any available server. There was an error on the way. Please fix it.
pakfire: DOWNLOAD INFO: HTTP-Status-Code: 500 - 500 Can’t connect to 443 (Connection timed out)
pakfire: DOWNLOAD INFO: 2.25-x86_64/lists/server-list.db has size of bytes
pakfire: DOWNLOAD INFO: Upstream proxy:

It looks like the test machine use pakfire through the proxy iam given but on my main ipfire i see that he tries a normal connection without proxy. Because its forbidden it doesnt function.

It seems thats a bug.