What happened with UPS?

Acronis

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Jul 15, 2009
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I have APC BX800ci-gr for almost two years. Until this accident I never had problems. It worked every time electricity went off. Also it happened often for electricity to be turned off for only one moment and in that situations UPS was always intervening perfectly.

This time, I left my PC and TV on (connected to UPS) and went in another room. I saw light went off so I immediately entered a room so I can save my work and turn it off safely, but PC was already turned off completely. At first I thought it was screensaver turned screen off, so I turned power button on but then I realized that PC was off because it started to boot.
What happened after couple of sec. It turned off again, and re-tried to turn-on. In that moment I swiched PSU button off as it obviously was something not going as it should.
Also, after some 30sec. UPS turned itself off completely. Ussualy it stays on even when I turn-off PC, so it can supply my router. (Usually it can work for hours supplying only router so I can have WIFI.)

What happened next is also strange. Electricity was returned after two hours, I turned everything on, and pressed PC button on, and my PC behaved as it woke-up from sleep mode!
I never turned hibernation on so I don’t know why and how that happened. (I use win.10)

Then I checked UPS and it shows as everything is normal, so why did UPS turned off PC and also turned itself completely? I even checked UPS self-test and it passed. I am puzzled about this. What should I expect from this UPS? Should I replace battery or take it to serviceshop?