RE: MMU2S keeps resetting/Red & Green LED's flashing at once.
I had a ton of issues with my mmu2 when i first set it up, i also ended up trying to fix the problem in all the wrong places due to the extremely poor or non existent feedback about what was going on.
I even bought a new controller board for the MMU but still same problems.
Eventually i found what the problem was, it was the idler drum that was rubbing against the left side and then the MMU probably got stuck with not able to rotate it and gave up.
And from memory (it was a while) i think the issue was one of the steps in the assembly instructions you had to use significant force to insert a rod or similar and if you got it wrong then the drum would rub against the side (plastic against plastic)
Once fixed, it solved all my strange issues and it has worked fine ever since (probably a year or two)
RE: MMU2S keeps resetting/Red & Green LED's flashing at once.
This change (lowering speed/power usage of servos) worked for about half a year, then the problem came back. I decided to try the hardware modification suggested here: https://forum.prusa3d.com/forum/original-prusa-i3-mmu2s-mmu2-hardware-firmware-and-software-help/i-found-serious-design-error-in-mmu2-electronics-hardware/paged/12/ (I shorted the Diode D1 with a jumper so I can easily enable/disable the change). This worked excellently, and I then also upgraded to the new firmware (which drives the MMU servos quite hard), no issues so far, multiple prints with multiple materials finishes without a single MMU hickup.