M&S bra, elastic tears

Have bought several T33 07434/8020 classic bras over the past eighteen months or so. I put my thumb through the first one doing it up the first time I wore it. I have now got holes in 5 of the bras in the elastic back next to the hooks. The newest bra is just a few weeks old, I've worn and washed it several times and it has started to hole on the stitched zigzag seam. I tried mending some of the others but they have frayed a lot.I went into a Marks store to show them and was told that I have been putting them on wrong and stretching them too much! I have been wearing a bra for 50 years and now I am being told not to do it up from behind but to do it up at the front and turn it around. I find it difficult to put my arms through if I put it on that way and anyway it doesn't have any instructions to say to do it that way!The store told me that it is the best selling bra and they have never had any complaints. Has anyone else experienced this?