Yeah I get what you’re trying to set up but I was somewhat thinking the signal quality might be at play.
That should (ideally) just be a matter of a MAC Clone but you report that didn’t avail the issue. You also said DNS & VPN isn’t in play so I’m really not sure how much more I could personally offer for help.
Do you have a length of Ethernet to attempt Ship WLWAN → Repeater → LAN → Laptop?
Beyond that, all I got is & it may not even be related: