Broken motherboard after screen replacement?

My Pixel 5a device fell and although the screen didn't have any visible cracks - it started doing problems. I took it to a professional lab that deals with Google phones (I didn't buy the phone in my country) and they replaced the screen with a new one.
The phone was good for two months, then suddenly one day (without falling or anything) - the screen started to flicker and I can't use it. I thought it was the store's fault so I took it back to them. After a few days, they tried to fix it (tried also a new screen), but they claim that the motherboard is broken (and it was not their fault related to their fix).
I just paid a lot of money two months ago and my phone is bricked? Does it make sense that a motherboard is ruined for no good reason? What are my options here?