Apc smart ups 1500 always bucks voltage

I have had a apc smart ups 1500 (tower) hooked up with two ags gx series batteries of 165 ah each. since about two days back the voltage buck light remains constantly on when the unit is on mains power. I used hyperterminal to reconfigure the unit, as my provider had already told me the procedure for battery calibration and other stuff.

The voltage at home and in the plug where ups is connected is 220 as reported by killawatt , volt meters etc. i have another smart ups which does not exhibit this behaviour when connected to the same plug and set of batteries

Here is the problem: if i switch the unit off and disconnect from mains and batteries the buck voltage light comes on as soon as i plug everything back in. All the configuration data is lost as well.

I have talked to my vendor and is asking me to bring the unit in which means a total travelling time of 4 hrs in a city plagued by the metro bus project

Any ideas what is the problem and Is this problem fixable at home?

Thanks in advance

I have a (partial) solution that seems to be working as far as the retention of config data is concerned. Rather than directly reprogramming the UPS i ran the apcfix utility which seems to have worked.

The buck function is (probably) doing its job as their are instances where the light does go off on its own.

I will post if i find anything more concrete.