True enough, and there's no telling when or how that seal got cracked. I might have cracked it by over-tightening my non-QCC1 HF weed burner, who knows? I didn't find out the seal was cracked until after I got the tank refilled...not the best time to discover a cracked seal. I tried to find a relacement seal online, but no such luck. Nowadays I take a flashlight when I exchange a tank and I inspect all the seals in the tanks before refilling. Just a heads up, FWIW.I know the exchange places are supposed to inspect and "internally" recertify every tank, but I think it is not as thorough as a regular state sanctioned inspection and is only good for the next sale of that tank. How well they actually do the inspections is another question, but I am sure they are monitored pretty good and open to lawsuits otherwise.
¯\_(ツ)_/¯I am sure those seals are one of the points of inspection when tanks are taken in for recertification. In fact, the recertification process may require them to be replaced regardless of condition.