Did as you suggested, so far no issue. I will try another busier endpoint.
Edit: My staff said the clock did not disappear like the key labels but actually froze. On my phone the clock and key labels have just totally disapeared but return when a key is pressed.
Nothing on the log which I was not expecting.
Update: The two endpoints on .67 have got the issues, mix of no labels and/or clock frozen.
Just changed phone systems here… all of the Sangoma S500 phones would have the screen go completely black after not being used for a while. Turned out to be the backlight dimming timeout - instead of lowering the brightness of the display, the display turned completely off. I simply set the backlight timeout to 0 to disable screen dimming and the problem disappeared.
Interesting tidbit is that the S305, S405, and S705 phones all behave normally and the problem only exists on the S500.