Thanks - obviously until the height is calibrated (which is where all this started!) the readings may be 'odd', you also need to clear any DTC's before the calibration is started.

If the FR airspring is leaking then that corner is likely not getting to full off-road height which would then be the cause of the high voltage reading compared with the LF. If the sensor was faulty then the vehicle wouldn't lower over time, it would just sit lower all the time.

Try the soapy water test again when the FR is as high as it will go, spraying around the fold at the bottom and on the tube behind it. Also spray soapy water on the top nut because if loose then air will escape and with the airspring having been replaced the nut might not have been tightened adequately.

Update: I actually pulled the link below from this site in research as the inability to calibrate just does not make any sense since I clear all fault codes prior to attempting calibration. I think the Foxwell NT510 which I have is good for everything but calibration feature as this post from D3Jon points out same error problem I am having preventing calibration to move forward with cross link valve function when trying to calibrate ride height. I may be stuck laying out the cash for Gap tool. Frustrating since Foxwell does 99% of everything else very well it seems. And, I use it all the time for my other vehicles. I only laid out $65 for the Rover Software package for it.
https://www.fullfatrr.com/forum/post590463.html

I ran through the height ranges a few more times & right front sensor voltage seemed to be behaving normally. Maybe that one high voltage reading in off road was a "one off". Also, now it is back to jumping from standard to Extended Mode and not settling into Off Road mode. Now what the heck is up with that one? Debating next step as purchasing Gap tool & try calibration and go from there. Ugh decisions...decisions.

GraemeS - thx for the tips & weighing in too. Access seems like it is a big challenge even with mirrors to be able to see that top nut if it is leaking? But, I think this could be an area of concern as it is reman unit. Any tips for that? When you speak of folds at the bottom with it extended I did not see any when I was last in there. Can you clarify? Are you referring to where very bottom of bag meets inner tube? Much appreciated.

Update: Replaced both front air spring strut assemblies with OEM from Atlantic British. Root issue seemed to be faulty passenger air strut assembly. As suspension fault/codes no more and vehicle riding very well and no sag/droop on that side any longer. I inspected the unit and couldn't really pinpoint any real cause upon removal. Other than some water was in the bag. They were remanufactured Arnotts that were removed, so it was a good move anyway getting new baseline condition quality units installed. I went & ordered GAP IId tool yesterday so I can perform calibrations. Noticed lower control arm bushings in need of replacement while doing this job so front-end remaining suspension rebuild next on the docket.

Thanks to all who helped me with this problem. Hopefully others can benefit from the troubleshooting journey down the road.