Outdoor solar/ups output voltage drop

Hello,

I have this outdoor ups, a chinesium product with great specs and has worked great but now it started outputting around 95v instead of the 220v like before. it also makes a weird kinda loose transformer humming. I've tried getting a datasheet or something from the manufactures but no luck...anybody has any idea what I should try and look at? or if there is some common component that is weak in these products etc...? When I switch on the inverter at the back sometimes it doesn't turn on and sometimes it does. There is a diod on the control board that lights up if the inverter is on. Relays work fine as I can hear them switching when I unplug the UPS. The passthrough mains works as well only that it outputs 93.5v now instead of 220v.

I've recorded a short video where you can hear the humming and see the diod that lights up when the inverter actually is on.

Not sure if it's the lighting, but can you have a closer look at the cap in your pic below?
The top kinda looks like it may be starting to bulge.

I checked all caps and they look ok...what do you think that noise is coming from...?

Just wanted to let you guys know I found the issue, it was one of the transistors that was shorted, A quick search on aliexpress and a few weeks later and the UPS is up and running