I think someone else had a similar problem. I'd attribute it to not being in 100% and blowing back out.
You get all of the old one out and the new one in all the way? It has to go in under the brass outer lip and also under the lip on the stem itself. If you look closely the outer edges are slightly angled. Ideally should go in with the larger end towards the bottom.
They are a tad softer so I've thought about maybe a small shot of some type of glue or something as well to make it more "permanent"
BigMatt's new design for the rebuildable one is probably the more deal way to go in the long run.
Note: While I would love to take credit for his work, I am not associated with Mad Customs!
Originally Posted by senghing27
You can contact BigMatt-MadCustoms in his MCB forum