Problem in an Energy Analyzer

Have you checked for any EMI or RF Interference?

Sounds like a mechanical problem with the switches. Poorly made switches can bring the best, most expensive device to its knees. Membrane switches are notorious for building up oxidation on the contacts. And, heavy duty switches are not the best choice for small signals either. But if the contacts are accessible, you may be able to clean them using some "contact cleaner".

Harmonics are likely to give you problems with excess voltage and current in the neutral line, cause nuisance circuit breaker trips, and reduced life on three phase motors, etc. But the specifics of your description suggest a multimeter type device that is not responding due to contaminated, oxidized, or just plain bad contacts in the switch.

If you had interference issues, I would expect to see changes to the display that occur without anyone pushing any buttons. Good luck with your troubleshooting!

Thanks for replying.

If that is any harmonic issue, a Nokian PF controller also installed there and has been working perfectly.

May be the problem is in push buttons. But display not only holds but also the values don't change as the current, power etc being change continuously.

May be, the Nokian PF Controller has got a good EMI/RF Suppression filter inside while your energy analiser may not have got any.