Why does the HP P2055dn printer go offline over the network?

Question

HP

Printer P2055dn, connected by cable to the office network, has DHCP static from the router.
Windows 10 systems, UPD PCL6 drivers latest version 6.9.0 from the official website., latest firmware from 2014.

Problem: The printer goes offline and does not print. Users are forced to reload it in order to print. It started randomly, nothing special about setting up the network and equipment did not change.

I tried to connect the printer through the search for a new printer, then it is visible via WSD through port 3910.
Tried on local IP, then 9100.
Tried to disable SNMP on the printer.
I tried to turn off the timeout on the printer (I set the idle timeout = 0 in the TCP / IP Parameters), I tried to set it to 60 seconds, now I set the maximum - 3600 seconds.
Updated the driver from 6.6.0 to 6.9.0
IPv6 protocol was blocked on the bridge of the router, now I removed the block for interest

Did not try to reset NVRAM (they say it should be done in extreme cases)
Did not try to change other parameters in the printer (there is some other timeout HTTP inactivity)

Ap. I re-uploaded the latest firmware, reset NVRAM, connected not via WSD, but via IP address through port 9100. Everything was ok for a few days, then the printer is no longer visible on the network - it does not ping, the web panel does not open. Users say that this happens after sending a multi-page document to the printer. It prints the first page and disappears from the network. If I distort the port on the router, nothing changes, it only helps to turn the power off and on. The link indicator on the printer's network card is on, but nothing else happens. The same 49.03D9 and 49.0640

Ap 2 appeared in the log. I changed places with another similar printer that worked via USB. For some time without problems, and then again this picture in the log:

Answer 1

I rolled back according to the instructions from the Internet to 20100308 firmware, not a single gap for a couple of months.

Answer 2

Formatter may well die
Try to reset NVRAM.

Answer 3

has DHCP static from the router.

What is it like?
Or the static address, or receives the address receives on DHCP.
It was similar with another printer: The DHCP address changed, the computers "lost" it. I registered statics for him - I registered a new address in the port settings on computers - everything is OK.