Not likely. The weld keeps the floor sealed, not hold it together. It's most likely acclimation or product failure. I've seen jobs where the substrate shrunk and caused this also. Concrete can shrink more than 1/4" every 20 feet....
The glue holds the floor down. All the weld does is make it watertight and more cleanly.
In hospitals many times the flooring will be welded in the OR's and sterile areas and just butted in the non-sterile areas.
As far as I can read I don't see any moisture issues being exhibited other than a high test using ancient probes. The complaint seems to be seams opening and thus bad heat welding. Perhaps I wasn't clear in my prior post.
My point is seams aren't held together with weld. The floor should stick just fine with the glue.
I actually used to install vinyl for years. Before heat welding. Funny thing when the chemical weld failed, the vinyl would shrink and curl at the seam. But heck what do I know.
Why would the vinyl shrink? Was water being introduced into the seam during cleaning operations?
All vinyl can shrink. The cheaper the vinyl the more it shrinks. The reason for this is not the vinyl. It is the fillers in the vinyl. Think of it like w/c ratio in concrete. The better concretes have less water and more concrete. The better Vinyls have MORE vinyl.
It is a big problem. Lots of vinyl installers always compression fit seams assuming that vinyl will shrink. The better vinyls call for a gap between seams before routing the vinyl as those products don't shrink.