Unfortunately I had a lot of problems when I had an Asus power supply of 450W it refused to give any backup and use to shut off upon power failure or loadshedding as you call it.I was forced to revert and get my old PSU re-installed to get this UPS working.Since then it has been working alright and 2 weeks or so ago I had fluctuations issues and everything from the fridges to the lights were fluctuating but my PC did not reset once thankfully.
Although I agree with Ali in terms of Alfa Digital problems because I had a previous model before the current one i.e the 5310 and that also had the same problem with my Asus power supply and refused to work.The Mediainc guy said that due to different frequency power supply our UPS will not support your PC. Although I feel he was cranking absolute bullshit to say the least I was forced to cling to this company because of cash shortage otherwise my first choice was APC too.
I really do not know about your actual problem but maybe mine has been resolved because I am using a generic power supply the ones that come default in Asus casings
. But whether in the near future it keeps on working I really cannot say anything about it. My recommendation is to buy APC 1KVA if you have any spare money!