Well, Pentair came to my pool today to examine the plaster issue and the 'stuff' aggregating in the pool. As I came to beleive from reading the referenced articles in my plaster thread, they also believe the nodules to be nothing more than a calcification from a few voids behind some cracks. Method of repairing the cracks with draining, cutting out plaster section, replastering, etc., and the resultant permanent color changes sounds like a worse solution than the problem.
Aggregated 'stuff' is unknown. They suspect DE but without doing a chemical analysis, hard to tell. Was instructed to tear down the filter and clean it thoroughly and inspect each and every part for any tears, holes, loss of pliability in the screens, etc. At the same time, since system would be off, check salt cell for any build-up on electrodes.
Did all of that and besides it being horrifically caked with DE, found nothing. No holes, no tears, no problems. So reassembled everything and now waiting for the auto fill to finish bringing it up to a level so that I can start the skimmers without cavitating the pump. Then I can add in DE. Was also advised to use less DE than what's been done in the past.
So what I learned on the fly was the complete filter disassembly and cleaning and reassembly. Previously, a pool service had done that. Really not that daunting of a task once you do it once.