If I may add something here Guys.
UK Shoemakers and Shoe repairers use a Contact Adhesive similar to a UK brand named 'Evo-Stik' to fix Soles in place during manufacture or repair. This would have been used on these boots before the Sole Edge is Rough Trimmed and then Stitched.
I speak from experience as a Shoe Repairer. Contact Adhesive has a 'Open Time' during which it will stick like the proverbial S*@t to a Blanket! If a Sole is attached outside (before or after) of this 'Open Time' it will not have the same Bond Strength. There are also other considerations. Contact Adhesive is applied to both Surfaces which must be clean and 'Scoured' to effect maximum grip for the adhesive.
If the Leather Mid-Sole is not scoured correctly, and perhaps with a worn Scouring Band, it is easy to 'Burn' the leather which effectively 'Seals' the leather surface. This can also affect the Bond strength.
I wouldn't suggest for a moment that Shoemakers would intentionally not follow correct procedure or technique, or indeed that may have been the case with this pair but with the best will in the world, mistakes are made.
This is an easy fix for a competent Shoe Repairer, although it would be important to be able to get as far in as possible to clean the area first. If it could not be cleaned and made good with adhesive, then opening the sole further would be required and Re-Stitching necessary. A replacement Sole could of course be fitted but not really necessary.
Whilst there is definitely some substance in Renn suggestion that Thermal Expansion between two different material may have caused the problems, it is highly likely that we as Repairers and Retailers of some of Englands Finest, would see many many more of this type of problem than we already do.
Just my thoughts Guys ;-)
Richard.
