Pictures from both k4lp and Blackhat6mike are of belt separations.
TPMS cannot provide advance warning of these structural failures.
What did your tire dealer say when presented with these failures?
The condition of belt separation is not the result of running low inflation. It is the result of the design and manufacturing process of the tires not using the latest knowledge in tire engineering. Material science has improved significantly over the past 15 years so the knowledge and information is out there. If however an RV MFG wants the lowest cost tires then using the more expensive 1st class materials and manufacturing process is not to be expected as the tire company will most likely use the lowest cost components and construction. In this case the RV manufacturer shares blame for selecting low cost tires of marginal or possibly unsafe constructions if these tires were provided by the RV MFG.
Your tire dealer should give you an adjustment for each tire that failed based on tread depth remaining.
RE NHTSA did you provide full DOT serial in the complaint form? Normally they do not ask for pictures with an initial complaint. You might want to provide your tire dealer with the complaint number from NHTSA. If necessary you can also file a complaint with NHTSA against the dealer for failing to adjust the tires and report the failure to the tire distributor. It is the dealer's responsibility to notify the importer/distributor of tire failures and the responsibility of importer/distributor to provide failure rate info to NHTSA.
Belt separations develop over months of service and are not the result of what happened over one or two trips. If you review my post on How To Inspect tires
and watch the video link in that post, you will learn what you can do to improve your odds of discovering the separation before the tire comes apart.
Other than selecting tires that offer 100% warranty for 3 years and always running the Max inflation molded on the tire sidewall there isn't much more you can do than annual "free spin" inspection and hope you discover a separation before the tire comes apart.