Problem with UPS during switching

i had this problem in my home. The home is powered by an inverter, to give power to a TV, a couple of lights, a fan. My computer's UPS was also on the output of this home UPS. i realised that it is not a good idea to have two UPSs in series, so ran a separate line from the mains to my computer's UPS. Problem solved.

i don't know if you have a similar situation. Good luck.

Is the battery in good condition?

Not all UPSs are created equally, unfortunately as the price falls so does the sophistication. If yours drops out on switching surges it may be one of the types that "protects" your equipment by switching off on severe overvoltages or fast-rise transients. More robust UPSs will be both charging the battery and running the inverter full-time off the DC charging current so when the AC is removed by other circuitry that senses critical line parameters like over/under-voltage, transients, etc. the inverter doesn't even know it and just keeps inverting, assuming of course that the batteries are in good shape.