I did have one "new" fabric shred in the wash. It was a black solid. I had bought two dark blues at the same time - same brand - and they washed up "beautifully". It took a long time to get all that black lint and thread out of my machine. Ugh.
If this were my project - I would just start over.
I know this thread is not about bleeding, but I have learned to wash everything washable before cutting it. I had given some of that black fabric to another member of the quilting group I was in - and she told me that it "shredded" - I thought I misunderstood her, and thought she said that it "bled".
Vickie Welsh has more than one blog about washing fabric to remove excess dye (or to see if the fabric is a bleeder) before cutting it. And also minimizing bleeds after assembly.
https://www.colorwaysbyvicki.com/sav...g-quilt.html#/
I am in the soak the fabrics (like colors together, in case one has bad manners) in hot water for several hours, wash gently, and dry the fabric
before cutting it group.
If you want to selvage the non-background pieces, you could pick it apart while you are watching TV - but you will also have to pick out the quilting.
I would contact the place where you purchased that fabric - show them your pictures, along with the sales receipt. I would at least try to get my money back - and you might save someone else from having the same problem.
If "that" fabric is shredding at almost every seam - I would not even try to fix it. Was it fraying a lot while you were sewing it?
PS: I also wash the batting (if it is washable) before using it.
Reasons: A: I prefer the flatter look.
B: I "assume" that the recipient may - or may not - know how to "properly" wash a quilt - and I want to know that what leaves me will "tolerate" most washings. I do fear bleach, burns, and tears.
C: Fabrics shrink at different rates - some hardly at all - some a lot.