mulitcolored square in top right corner of your screen was indicator of undervoltage (I'm not sure about overheating).
But it has changed recently, now it's a BOLT icon and THERMOMETER icon - https://www.raspberrypi.org/forums/viewtopic.php?f=29&t=82373
ahh ok yeah i remember now...I was having that problem with my pi1..broke my power supply..no really had to solder it! couldn't go out and grab solder that day..so I used my cell phone charger..worked ok...after I got my other charger..but every so often that square would pop up for a half second.
according to the page you linked. It seems ok once it goes away..it was there for a half second. I think I had forgotten to plug the power into the hub..so the pi was powering it till I got the power plugged in.
also see this article: http://makezine.com/2016/03/02/raspberry-pi-3-not-halt-catch-fire/
max operating (official) temperature for pi is 85 C (celsius)
but there are know samples running close to 100 'C
Maybe you just have a lemon. Mine is running around 70 'C without any heatsinks or fans - but it is when playing movies on KODI, not with AM.
Maybe you can just make a quick check if it's a software or hardware problem.
Just download LibreELEC image flash it to SD and play a movie. If the temp are still high this could be a hardware problem.
ok that's good to know thanks verion..I looked "everywhere" for that I never could find it. actually I have ran kodi on on it. Runs normal even with kodi..a little hot as to be expected. Although I did read and article somewhere and after doing tests with a termal camera it was the Ethernet chip that got the most hot. Makes sense there as that is "intensive" when "on demand" like that.
So how hot is the rasp pi4 gonna be? as far as I've read they are running into the thermal barrier on cell phones (which the pi is) fast.
Funny how after 40 years we've come back around to risc cpus and fan-less single board computers...we were doing that 40 years ago..I miss my commodore64!