You can try adjusting the carto. Unbend a paperclip and put it in the center of the carto to pull it down slightly.
I don't have this problem with my Prodigy, but I
do use this technique for some of my other PVs. What actually works perfectly is one of the silver pieces of the large binder clips.
They fit perfectly snug in the carto hole and pull it down with ease. I find that my Prodigy does the opposite: the center pin on the adapter is so protruded, that it will push the center pin of my cartos in too far for my other PVs and they don't fire. For those of you with Prodigies, try getting a blunt object (I use a Sharpie) and
firmly push on the disc beneath the top adapter. Sometimes, screwing in a carto too tight will force your center pin down, and all it needs is a firm push back up. To the OP, I think this may be your problem since some of your cartos aren't firing. Of course, try what swedish is recommending first, and get the center pin of your cartos to stick out a little, about half a mm out. This will ensure proper contact with the Prodigy's positive pin.