***Update***
Thursday night I didn't have any success fixing up the 14mm nut on the top of the strut so I had to wait until morning to get a new one.
Since I had the time, I removed the strut assembly to clean/inspect for damage and lube the o-rings that seal the bag.
I found the top two o-rings rolled and cut, one of the two plastic rings smashed, the main shaft (that the 14mm nut threads onto) worn badly on one side, and WORST OF ALL the cause of all this failure.

Although the instructions on the Arnott website are perfectly clear, they were not followed when the original repair was made. The "puck" that sits atop the airbag and gets compressed in with the 14mm nut was installed upside-down. It looks like it should go in that way but it will never seal properly (which it didn't).

Soooo, rather than call up Arnott and order another strut as my first impulse told me to do. I decided to try and see if I could salvage this one or at least make it through the weekend. I got new o-rings for the top, lubed the two at the bottom, put it all back together with the puck right-side-up and torqued the new nut to 55 ft/lb. It's now after midnight on Tuesday and my air suspension has been sitting perfectly level since Friday morning. The self level inact. light is still on and the switch just blinks 3 times when pressed but at least I'm holding pressure now.

I still have active codes for the valve and pressure sensors but I doubt they are accurate. I replaced the reservoir sensor with a new one and there was no change. I'm guessing either a damaged wire or the module has failed.

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2005 4.8is