Radio Popper PX & Canon 550?

Anyone have any experience with this combination? I purchased the PX system for my 550's a few months ago and have used it a few times when I thought ETTL would make life easier. However I have had an issue with the flash not firing consistently. I thought it was the connection to the flash and ordered a new rubber isolation cushion. However a friend of mine recently purchased the same combination and he called me with the same issue.

Is there a known problem with the PX and the 550? I have used the JrX extensively and never had a misfire using the same (2) 550 flashes.

I attended a workshop with TriCoast Photography here in Houston, Texas on utilizing the Radio Poppers and I had the 550's and they felt for some reason that Channel 4 worked best on the 550's. During the whole 3 day workshop, I never had a single failed shot.....

Never tried Channel 4. Not sure why this would be an solution , but thanks.

Jim

Something about that particular channel or frequency being cleaner.....