I got the same/similar problem with my Librem 13v2 here. There is another thread on here that might be interesting for you: Terrible wifi performance with librem13v2
I did open my Purism and checked the antennas. Connectors were okay, but the cables are curving around on the board before being routed into the LCD part. Due to being fixed with tape on the board on several points they were getting some stress when opening the LCD, because the movement is pulling on the cables. I loosened some of the tapes to relieve the stress but I don’t think this changed much.
What I understood is that since the aluminum backs are shielding the antennas the only area where they can actually receive well is along the hinge below the LCD. So far I can only assume that this is the reason why connection quality drops so fast with growing distance from the router and when pointing the laptop into another direction. If anyone got other ideas I’d welcome them.