I'm wondering why there was a lot of stress on the fabric? It seems like I remember unsticking something and I didn't do the whole thing at once, I did it one iron or half iron sized area at a time, lifting the iron and immediately beginning the peel. After I had the edge loosened, I left the iron on it. As I lifted the edge, it would slide the iron over to a new spot.
I find it ironic (see what I did there?) that I frequently have iron on stuff come unbonded because of using too high a temperature. If I want to remove it, it's on forever, but if I want it to stay forever? Oh, noooo...