I am also investigating if Chromium trying to (automatically) upgrade may disturb a Node-RED dashboard application. Trying to find out how to disable these annoying upgrade messages too. I already upgraded Chromium a few days ago but the message appeared again today.
This application runs in a Raspberry Pi with the Desktop version of Raspian. It is a kiosk type application. I just added an ui_control node to monitor the connection from the runtime to the dashboard. Perhaps this kind of monitoring can help you too ?
I see quite a lot of connection lost messages in the debug node.
What I find strange is that the screen is connected directly to the Raspberry Pi that runs the runtime. I can not imagine how come that the websocket between Chromium and the runtime could eventually be lost. There is no way that this can be a network issue.
10 minutes after relaunch Chromium the connection lost messages are gone. I will keep monitoring. Apparently (initial assumption) is that disconnections occur whenever Chromium displays the upgrade/relaunch warning.