RF640 Freezing

[BunnyOne]

Hello,

One on my Roland RF 640, is freezing. Stop printing, even in sleep mode, impossible to shutdown with power button. I had to switch off, wait 15 seconds and switch on.
It's totally random, I could print 5 minuts, 5 hours, or 10 seconds.

Any Ideas ?
Thank's !

 

[Roland Certified Tech]

What message comes on the screen if any?
Sounds like a stuck key on the panel. Wiggle all of them of remove the top piece.
Keys can be checked in Service Mode.