Help diagnosing a bad print with multiple shifts and missing section of some layers  

Help diagnosing a bad print with multiple shifts and missing section of some layers

So, I have been printing with my MK4 and MMU3 for a few months now, and things have been going well overall. I have had the normal issues every once in a while that I need to troubleshoot, but this one is new and seems very strange to me. I had just finished a print using two colors  (black and red PETG) and started this single-color print (the same black PETG) that had almost a full plate of various items on it, including one large item.

I stopped the print a little while in, because it looked like this:

It is apparent that there was a layer shift for some reason, but the stringing between layers seems very strange. When I took this off the bed and looked at both sides, I think I saw where the initial issue might have occurred, and I have a suspicion about what caused the stringing.

FRONT:

BACK:

From the front on the light surface, you can pretty easily see through what should be a solid object. When I flip it over, it looks like the extruder lost its mind, which can be seen in more detail with this closeup of the bottom/back of the failed print.

Does anyone have any ideas of what might have caused this to go so haywire?

Thanks,

Sean