Did you have them cut it to a custom shape, or did you just have a simple rectangle cut to size? Just curious because in 25+ purchases I have never had a single problem with them, although I patronize the San Mateo store.
Also, at TAP I'll always go for the paper backed cast Acrylite GP... it's always machines waaay better for me and I've never had a problem working with 1/8" GP, whereas I have had a couple issues in the past when working with the more economical plastic backed FF series in 1/8".
The FF sheets seem to never be perfect either, with what little protection the thin plastic offers.