hi,
that's what support told me :
1-
A good place to start would be to reseat the ribbon cable connector which runs between the front panel and main PC boards. The process to do so is easy, requires no more than a screwdriver to perform, and we have detailed instructions for doing so at the following link.
http://www.davesmithinstruments.com/tempest-panel-board-removal/Just follow steps 2-4 to open the enclosure and reseat the ribbon cable connector. Please remove and reseat both sides of the cable. Reassemble the Tempest in the reverse order of disassembly and check whether the issue you noted is still present.
2-
The next thing to try would be to perform a button cleaning routine on any button which is displaying intermittent operation. The switches on our instruments are self cleaning and the process to clean the buttons requires no tools. Simply press the button 50-100 times with a great amount of force. This usually clears up any intermittent/non operation. If you find the button's response improves, but is still somewhat intermittent, try performing the button cleaning routine again. To note, there is no calibration procedure related to the buttons' operation.
for me it was still the same.
but really .. later i had some long session i was days working with the tempest and it seemed to work better. if you don't use it often or leave it for months it can do this i guess. It's cheap quality buttons.