Cannot update template when connected to Openwrt router

Hi , I’m new to Qubes.

I installed Qubes on a laptop, connected to internet via lan from a 4G router with openwrt firmware.

My Debian template (fedora too) cannot be updated via the GUI updater. Manually doing sudo apt update from the debian-10 template for example, gives the following error:

Invalid response from proxy: HTTP/1.0 500 Unable to connect  Server: tinyproxy/1.10.0  Content-Type: text/html  Connection: close     [IP: 8082]

Any appVM based on the template can access internet perfectly. sys-net is defined as updateVM for non-whonix templates in /etc/qubes-rpc/policy/qubes.UpdatesProxy.

Connecting the Qubes machine to other network (such as wireless hotspot created from my phone) removes this problem.

Could this be related to tinyproxy configuration or something in the router blocking the tinyproxy? Any help appreciated