Hi Sunshinegirl,
You’ve certainly had your share of issues with your PLB mattresses.
Latex International (now Talalay Global) was having a higher than average number of quality control issues a couple of years ago (see here and here) which they seem to have resolved so this may have been the reason for your first defective mattress.
Having said that … your replacement mattress certainly shouldn’t be sagging after only three weeks and it seems you have eliminated the possibility of it being a foundation issue so if you have measured visible impressions that are an inch deep (with a tight string or a straight edge across the mattress surface) then it seems that you have a defective mattress once again and unfortunately you would need to go through the warranty process again.
Just out of curiosity … what is the manufacturing date on the law tag?
The all natural is less durable than the blend … especially in lower ILD’s … but it sounds like your issue is a defect anyway not a result of the blend of latex.
There is more about glued vs unglued layers in post #15 here but it’s really a moot point since you wouldn’t be able to get a refund with a warranty replacement anyway.
Latex is very flexible so bending the mattress during delivery certainly wouldn’t cause an issue.
Unfortunately it seems that you have another defective mattress.
Phoenix