CAT6 network cable break in front of the network socket?

CAT6 network cables were laid under the plaster in the old terraced house.

Today I set up a patch panel with the respective network cables.

Unfortunately, for the most relevant cable (gamer PC), only 6 out of 8 wires are shown to be working using the tester.

I secured all the wires, including those in the box, with a crimping tool and pressed them in again. I laid the original Type A wiring in the double box from left to right in the box. Type A wiring in the patch panel, too, of course.

The error remains.

Unfortunately, the network cable in question is not in the conduit, but plastered over and is so short that I cannot conduct any major experiments with it.

Is the cable broken? How do I determine this more precisely?

Thanks for tips.