In situations such as this there are obviously quality issues involved. Did they change sources? Did the original source change designs without approval? Or, was the original source told to change specifications? Not being able to evaluate the problem cap(s) it is hard to understand the root cause. Here's another scenario: Some unreinforced plastics will distort under temperature, affecting sealing (or venting) surfaces. A way to dimensionally stabilize plastics is to reinforce the resin with materials such as fiberglass. However, doing so really makes the resin abrasive, decreasing the mold life dramatically----and molds aren't cheap. It then becomes a crap shoot---save a few cents a cap, run the risk of having some defective units shipped. This is just speculation and an example, of course.
Regards,
Michael A
Cypress, Texas
