Question PC restarts when power comes back despite having UPS

[Utsho]

I am facing this issue for months.
https://drive.google.com/file/d/17VkbWxa4Pr4kFUT91_GwFEzIc1fAa1M8/view?usp=drivesdk
It was fine before, my PC reboots when main power comes back online, it works fine on UPS battery I mean when main power goes off it runs on battery didn't face any restart, but when main power comes back PC restarts.
Also I noticed another thing ups used to make a clicking sound when voltage spikes but now it doesn't.
but when UPS makes that clicking sound without any voltage spikes PC restarts.

I sent it to the warranty but eventually they just changed the battery, but the problem was the board itself, i sent it again but they didn't change the board, they were just texting with their pc and said didn't faced any restart and sent it back.
I saw their pc, they're using a super low not more than 100w components,
And I'm running a gaming setup with rx 590.
Let me be clear on this that even I'm in bios (that doesn't pull much power) and turn the main power off an on pc restarts when i turn on the main power.
I have another UPS, i was using it while another one was under warranty, after couple of weeks this one is also facing the same problem.
So I was guessing maybe it is a delaying issue, but if it was delaying issue then it should make that clicking sound when voltage spikes.
Note that this doesn't happen all the time, if i turn main power off and on, it restarts 5out of 10times.
The UPS is powerguard 1200va
And thermaltake smart se 630W psu (it's new, it'll be one year this January)
So my question is what is the problem here?
And what is causing both UPS to be falty the same way?

 

[john2376]

I am new to this "DIY with electricity" and all that, so my respond might be useless,.. But with what you have said, have you tested with any equipment say a multimeter just to see if the current stays stable when power is restarted?
For if even a small variance in stability between say the UPS and the power supply occurs, it is likely to reboot.
I'm not very familiar with how an UPS works, but I would assume that there is a circuit that detect a loss of incoming power and thus switches over to drawing current from the UPS's batteries, inverting the current and stepping up then delivering it to the UPS output going towards the computer PSU, could it simply be that the detection/monitoring circuit is too slow when it switches back?
As I said, I'm not familiar with this sorts of things, so I just tried to imagining what could be the issue/cause of the trouble.

 

[Mr.Spock]

could be one of two things - some APFC power supplies may not play well with simulated sine wave PSUs or the transfer time of the UPS is just marginal (which is what you alluded to) - however that usually presents in cutting over to UPS and not back. some UPSes can detect a "hot" line and won't return to street power until the voltage is closer to spec and you may want to check if that's configurable via software in your case