Cant edit blocks after few seconds in panel

One of my client, cant edit blocks after few seconds in panel. After login into panel is everything fine, but after the block edits icon change to trash icon only. When I try connect from my computer, everything is fine. Any idea what could help? I tried delete media folder and update to last 3.5.2 RC version, but without success. He tried different browsers and has updated Win 10 system.

Hello and welcome to our forum!

Any error messages in the console that could help debug this?

Same here with a Windows User @ Kirby Can’t provide more details at this moment but will try to get more info from the Console.