Ah. Maybe that's what it was. Well, it's over now. I pulled it out and put in in a few times to see if I could loosen things up. I looked at the ring end gap in the exhaust port and it looked fine. But it was still pretty sticky when going above the exhaust port. Finally, when I was pulling it back out it came fast at the end and the top ring must have caught on something as it exited the cylinder. Cracked a 3/8" chunk out of it. Ring is no more.
The good news is that with only one right it slips in and rotates just fine. Regardless of whether that one ring is in the top or bottom groove. So something was definitely up with the one ring. Anyway, I'll need to find a new ring now and get back to it later.
Walter - How did you reduce the ring width? I assume this means slightly increasing the inside diameter of the ring, right? Did you just use a grinding wheel or sanding disc on a dremel and free-hand it around the inside of the ring?
Really appreciate the guidance folks!
Thanks,
Rob