We have a SV8100 system running with UX5000 phones. (Upgraded the back end years ago and they kept their phones)

The system has ran flawless for years. Now I'm having misc phones loose their displays. Sometimes you can unplug them and reconnect and they'll come back. Sometimes they don't, but if you try them on another system. (Bench system at our office) They pop right on. I've replaced with new to them phones and within a few days they go out as well.

Anyone else see such a thing?

Have you re-booted the main system? Also, if they are using email-voicemail make sure this is working and that all the emails are up to date. Replace battery on the processor. I have seem this when, what I suggested AND if the main processor is getting DOS attacks.

This system is pretty basic. No outside connections.
The last thing I did was pull the blade and deleted the slot then replaced with a new blade. So far so good. Fingers crossed.