WindowServer crashes on OSX 10.11

My macmini started to "logout" randomly, until now I could only find a LOG relevante input, which I can not decipher!

"Logout", the screen goes to Login authentication page, but in reality all the open Apps keeps running in the background.

Also I have re-checked, sleeping time for Display or Hard Disk are set off, as well no screen-saver activate nor the nap function.

The Macmini is 24h running and connected with HDMI to a AVR system, nevertheless it happens always when the screen is off.

here is the crash entry line:

03/06/20 00:01:29,730 ReportCrash[1039] com.apple.message.domain: com.apple.crashreporter.writereport.crash

com.apple.message.signature: WindowServer

com.apple.message.signature2: UNBUNDLED ||| ??? (1)

com.apple.message.signature3: 185C0CC23C38C57A4C6DFF52029DA46E

com.apple.message.result: NO

com.apple.message.summarize: YES

SenderMachUUID: F111FB16-C83B-3CBE-BE8B-88B4447B4927

Any help it would be welcome, thanks in advance for your trying out.

Miguel