CMU200 repair

[Avinoam]

My CMU200 bottons on panel stops to work after I push "RF CONNECTION CONTROL" botton . I have to OFF , and ON again the unit .
No erors in self check . The analyzer and generator are working O.K.
Can you give advice what to try ?
With versionmanager I tried to load program version V5.12 , and 5.10 , it is the same .

I load version V3.5 and now its working good .
How can I use the internal speaker ? nothing in the manual .