O2 sensor shifted it's output range during operation - bad?

I was able to take my first drive with my new engine combo and twEECer use. I had been having problems with my O2 sensor. (see - http://tweecer.oplnk.net/viewtopic.php?t=2883 )

After reviewing my datalog, I discovered HEGO1 shifted it's output voltage range in the middle of the trip. It started out switching between 0.2V - 0.8V and then suddenly (at ~760sec into datalog) it's range shifted up so that it switched between 0.6V - 1.2V for the rest of the trip (total trip = about 40 mins). It also seemed to switch less often after this happened.

Here's a screenshot showing how the O2 shifted it's range - http://home.mchsi.com/~neocarjukebox/040531151055-a.jpg

And a closeup - http://home.mchsi.com/~neocarjukebox/040531151055-b.jpg

BLUE = HEGO1
YELLOW = HEGO2
GREEN = RPM
RED = PLX WB logged data

Is this normal?!?!

Elaborated:

I disabled adaptive and forced OL at idle for this drive. Of course, idle was 14-16 (on the PLX) but when I'd accelerate (then into CL, I assume), sometimes it would go rich, like 12ish beacuse of the 'stuck' lean O2. Other times it would go lean, about 19 beacuse of the O2 stuck rich. I'm not sure why it would choose one over the other??

WB sensor is in pass. side bank (that's HEGO1's side, right?). O2's are new.



Thanks,
Rick

Can anyone advise me on this? I don't specifically need tuning/TwEECer advice, just O2 sensor help. I'm wondering if this is a 'hardware' problem rather than a 'software' problem. It almost seems like a bad ground reference.

Rick