I've been selling the Flushmate since 1996
I talked to the folks at Sloan Flushmate about it. They say there was a very small number of returns for that. Very very small.
I do recall replacing an old tank about eight years ago, that had split at the seam. If the seam splits and releases slowly, then it's just a leaking tank. Their complaint was that it was no longer holding water.
Sloan started putting a pressure regualator on the 2008 and newer tanks.