@Mewwwttt 

Hi,

Here is the thing: what you are experiencing is a classic case of hardware/signal incompatibility between the router's port and that specific cable, even though they work fine separately.
Newer multi-gig routers (like your Archer BE3600) have highly sensitive ports that require strict signal integrity. Other routers are usually more forgiving and will accept a weaker signal, which is why the cable works on them.
Why this happens:

1. Port Sensitivity: The TP-Link port is likely detecting micro-interferences or a slight voltage drop in that cable that other devices just ignore.
2. Wiring Standard: Even after reclamping, if the internal wire order doesn't perfectly follow the T568B standard on both ends, this specific router might refuse to handshake with it.

The Fix:
Since you already tried reclamping and it didn't help, don't waste more time on that specific cable. The internal copper or shielding is simply not up to par for this router.
Your best and quickest move is to swap that cable entirely for a fresh, high-quality Cat6 or Cat6A patch cord. That should clear up the LoS red light instantly.