On my old phone I had an issue with the proximity sensor and front facing camera. This led me to holding my phone backwards to take photos and being unable to hang up phone calls.
I think I put up with this for a year and a half.
I did end up figuring out the issue with the proximity sensor but opening up my phone to reconnect the camera module was too much effort for me.
So ups have AVR (automatic voltage regulation), that is a big part of the selling point. The power that they output is “clean”. One of these is basically AVR without the battery.
It’s not quite as good as a good ups+AVR, but it’s a fuckload cheaper and you don’t have to replace the batteries every 6 months.