Hi campr-pete,
You're right that your documentation doesn't warn you about delamination as a possible consequence of caulking/sealant issues. But neither does it warn you that if you fail to lube the wheel bearings annually, that a wheel may fall off.
Your delamination may or may not be caused by water intrusion, but sealants/caulking need to be checked frequently to prevent water intrusion.
If you re-check your owners manual, you'll find that there's a maintenance checklist that spells out the need to check roof and sidewall sealants every 3 months along with seals, windows, doors, etc. Here's a screen capture of part of a recent checklist.
And if you re-read the warranty statement, you'll find that warranty doesn't cover issues arising out of maintenance issues. It probably says something like:
The owner is responsible for proper maintenance ......Failure of any product or component caused by improper care,
cleaning procedures, negligence or faulty maintenance is expressly excluded from this warranty.
However, it also probably says something like:
The independent Heartland RV dealer, by agreement with Heartland RV, will maintain the recreational vehicle until it is
sold to the first retail customer
If you look at the date of manufacture on the large white label that's affixed to the frame at the front, on the doorside, you'll have an approximation of how long the trailer sate on the dealer lot. If the dealer had it for an extended period, you might reasonably ask if responsibility for early-life maintenance-related damage actually rests with the dealer.