I know just what you mean !
M&S has always been my go to for knickers for quality, fit and comfort and the fact that for some time they were one of the few places that actually sold multi packs.
Decided my undies needed replacing so bought 2packs knickers plus 2 packs of the multipack bras.
I only opened one pack of the knickers and after only 6 months the seams are coming apart.
Of the bras, I had one pack that were plain cotton that were soooo comfortable, I was thinking of buying more - until I wore the second one in the pack.
The underwire started poking through so it looked as if I had 3 boobs by the middle of the afternoon (not a good look when wearing a t shirt!) .
I complained to customer service by email and all I got was a reply saying "Thanks for letting us know, we will let our quality control dept know"
I have long thought that as soon as M&S started using overseas industries to produce their products , that the quality had fallen for most things and wonder how many millions they lost over the years by having to refund for items of bad quality ?
My ex husband works in textiles in China and has often said that he frequently gets in trouble with the company directors over the amount of stock being made that he returns to the factory - they seem to have no concept of actual quality control - you show them the standard and after a short time they slip back into the unacceptable.
Not the worker's fault - they are often paid per item rather than on the finish , so rush and make mistakes.
Maybe it is also our fault for wanting to have cheap clothing!