Connection box in the wall - What kind of connections are these?

The nonsense about shielding-related issues making it unusable, forget it

I beg to differ here. I have crimped too many network cables myself to have learned that shielding not properly threaded onto the connector makes the difference between "works only with difficulty over a short distance" and "works over any length as 1000Mbit."

It might be different on the way to the TAE, since there is enough voltage on the network side and the notorious bell wire really suffices. In the intranet, however, the transmission technology is different.

I have already crimped too many network cables myself to have learned that a shielding not properly threaded into the connector makes the difference between "works only laboriously over short distances" and "works at any length as 1000Mbit"

I don’t fully understand it myself, as the phenomenon seems illogical to me: but the way you describe it, I know it from patch cables and their connector transitions as well, though installation cables seem to be more tolerant in this respect, even though it theoretically shouldn’t be due to the distribution alone. In any case, I have seen plenty of runs work perfectly in practice, which I wouldn’t have trusted at all theoretically.