Freezes, glitching screen, boot screen fade-out and boot loops

I’m on a bit of troubleshooting spree lately. I have a Samsung S6 Edge+ that I pretty much threw aside after it malfunctioned . It’s been sitting idle for over a year.

Today, I decided to try and take a closer look at it as I got some tools recently that allow me to open up the phone.

This phone seems to have multiple issues that are quite inconsistent.

Here’s what it does:

• Freezes on the “Powered by Android” screen - this is what it mostly did. I would always fiddle about with it (flash firmware) or leave it alone, and it’d sometimes move past that screen and try to boot. It was on this screen for the longest time and only today did it finally move past it. I opened up the phone, removed some connectors and even took the board out. I then put everything together again and it started booting up. It hasn’t got stuck on this screen since I opened up the phone.
• While in use, if I manage to get into the actual OS, it would randomly either freeze and then enter a boot loop, getting stuck on the animated “Samsung” logo after some time (usually when the buttons light up), or the screen itself would massively glitch out, freeze and then boot loop (sometimes giving up entirely and switching itself off).
• The “Powered by Android” screen is faded out. I can see it in faded form onthe right backgrounds (i.e Odin mode, or home screen).
• Sometimes it will just freeze without any visual anomalies. For example, when I was flashing firmware, It’d commonly get into the setup part and then randomly freeze completely and reboot. It is sometimes accompanied by visual problems, however.

Sometimes, like today, it will work as if nothing is wrong (apart from seeing the faded boot screen). It lasted about 4 hours today and is now back on a boot loop, sometimes making it to the home screen, quickly freezing and rebooting soon after.

My suspicion is maybe the GPU is faulty? That would possibly explain the screen glitches. It crashed quickly when I tried running a benchmark (3DMark). Since I ran that, it has been struggling to stay on the OS.

If it is the GPU, replacing the main logic board should resolve it, right?

My other suspicion is the screen itself. Could that be faulty, enough to cause all the problems I’m describing?