shell molding issues

Can anyone tell me why I might have 50% of my shell molds pop out beautifully, and the other 50% break within the same tray?  My thought is that because I bought these used, perhaps some cavities were cleaned out with something abrasive?  Sometimes the entire circumference breaks, sometimes just a piece at the top.  But I always get some portion of the molds that are perfect.

It sounds like your chocolate is too thin.  Try making the chocolate shell a bit thicker.  Also, are you using cotton balls to wipe out your molds prior to use? 

Hi Andrea!  No, I have never cleaned with cotton balls, only a soft cloth.  Unfortunately, with all the breakage, I've had to wash them (only with hot water) a million times, which I've read (somewhere) is not recommended.

I'll let them set up a little longer, although I have to say that I fear shells becoming too thick.  Clearly, I'm on the wrong path right now, though!

Thank you!