Thanx for attention and advice.
I've posted the message to client area.
Here is the copy of the message, people must know
http://forum.ispsystem.com/showthread.php?t=2928
What access do you need?
ISPManager HTTP interface admin access, ISPManager HTTP interface user access, SSH user access, SSH root...?
There is a big and important project at the server, we are interested to give you minimal access...
Here is today Zabbix graph
[ Trying to upload... Unsuccess. I compressed images to pointed size, height and width and still see "Close this window Manage Attachments | Upload Errors | 2017032705.jpg: This is not a valid image file."]
I did almost (but not!) the same: ISPManager admin login, down to the same user account, File manager, /logs, download access log file, logout 3 min max.
Today I think, that it's not important what to do under user account (see forum thread).
Our system administrator killed some process (I don't know exactly what process) and situation normalized exactly at kill time (see graph).