The ones I see coming into the shop are usually about a year or two old and the soles are turning into a sticky powder-like consistency. That in and of itself isnt the problem but because the uppers are attached to the insole by a thin very exposed thread that has been melted into the now crumbling sole I can't remove enough of the old material to get any suitable adhesives to stick without cutting that structurally fundamental stitch.

The sneakers might hold up better but must just not hold up well enough for folks to bring them to me