Questions about Kyocera M5526cdw Ecosys incl. toner TK-5240K

In c't 6/2021 on page 52 under the title "Garantieverschleppung - Kyocera verschleiert Schwachstelle" a systematic problem is apparently described. Stripes are said to appear from approx. 5000 pages onwards because a screw for the removal of toner is worn out on a spring. There is also a link to a video in Russian that is well made and a forum (ct.de/y8d3). Is it known whether the problem described still occurs as standard? Have other buyers also had this problem?

Why is this machine including toner (CHF 535.--) cheaper than the same machine without toner (CHF 598.--)? Or are the two devices not identical?

Which is the correct 2nd paper tray for this printer. i find - Kyocera 2nd paper tray PF-1100, 250 sheets; sheets. Supported support weight is 60 to 163 g/m². Accepted media types: A4, A5, A6 - Kyocera 023R60UN; no information about the Paperhandlich I need a model where I can load the thickest paper possible.

Guarantee: the description does not state a guarantee. Isn't a 24-month guarantee required by law?

Kyocera toner return service: Is this also possible if I buy the device from digitec? Is there an extended warranty for this machine? What does it include? What does it cost?