Problem with StatPanel

Hi guys!
I use Grafana v6.6.0.
Somedays ago i found this trouble with stat panel. This panel displays data from Zabbix server.

I cant find the reason why panel is “disappeared” from dashboard. I checked it in different browsers, nothing helps.
There is a hint: when i click on panel settings - Title “Transparent” - i can see my panel, but only for a short time before F5.

This is how it should be:
I have tried to replace the panel, to add new stat panel and nothing helps. Maybe smb knows what the reason?
Thanks in advance:)