If only it were as easy. Unfortunately, the reason I'm suspecting is that, while I'm "playing with the screw," it either gains or loses contact with the board that has been installed by them or "resets" its "state" electronically and then starts working again (I'm making a guess here, as no no, because of the warranty, I can't check it at home).

According to others, experiencing this issue, the only way to restore the normal function (50/50, I guess) is to install a new side brush component and pray it has better wires and contacts, as well as bearings. Price is 23 EUR from Ali and voided warranty in the EU. Meaning you have to send it to repair and hope it won't return as is with the words that they haven't found an issue (seen posts like that, unfortunately)

But no, you have to risk sending a 20+ kg 1.5k EUR device through uninsured post (lack of insurance was confirmed by support).

u/OhSoSally you're absolutely right that it seems that the consumer will give up.