OK. So.

I had my clogged arm - it's the plastic piece with the hole at the top that has the lever at the end. Qidi is sending me a replacement - presumably just for that piece. So, since I had a replacement on the way I decided to really put some effort into it, got a bigger drill bit, and opened up the hole. The problem was, basically, I had a C-shaped piece still in there, and it didn't leave enough room for a piece of 1.75mm filament to go through.

I reassembled, did a filament load, and filament flowed normally.

Then I tried to print, and ended up with a mess. A little getting laid down, and a lot getting dragged all over the place. Re-leveled. Tried again. Same thing.

I did that a few times, all spectacular failures.

Then I did a print from the left printhead. And it's looking pretty close to perfect.

So, any thoughts on what I could have wrong with the right printhead? I can't have it mis-leveled or anything. At least I can't see HOW I could manage that.