Hi Marek_PL,
Thank you for using the Support Forum. Please try disabling the the bi-directional communication in the driver and see if that will fix the issue. Please see this article for information on how to disable bi-directional communication on the port. In the article it says to enable you will disable. If that does not help please consider contacting you local support centre for additional assistance.
In some days printer start printing by itself pages with exception report though any printer jobs aren't send to printer. Printer prints 2-10 redundant pages per hour. At this time I can print documents by Wifi or Google Cloud Print Service. Printer is connected only by Wi-Fi. Printer has latest drivers.
printed error pages text:
Exception Report
Model Name : Phaser 3020
Machine serial Number :52961XXXXXX
Host Name : Xerox_3020
Firmware version : V.3.50.02.01 JUN-31-2018 (P3020)
Assert Log Information
Assertion failed:
file ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿ"