The stone bothering my gall bladder came out on flush 2..At flush 4 I was only getting sludge- no stones. I waited about 8 months and then did another flush which I got more pea sized stones and then a week later did #6 which produced a number of large stones. I don't know if you are using the formula with the Epsom Salts or not, but it does help to open the tubes so that the stones move more freely. Also, since it is bile pressure that actually moves the stones, you might try taking a milk thistle or other liver support supplement for a month or so to increase bile flow and then try again. If you have had blockages for a long time, your bile flow could be very low. You can also cut your fat and protein a full 24 hours before your flush to make sure the "pump is fully primed". If your gall bladder if really full, it make take a few attempts to expel them all. The stones take up the space that the bile would occupy. But you can expel stones from both at the same time, to answer your question.
It's great that your son has success and at 21, I'm sure it is an eye opener. But everyone's plumbing is different so please don't be discouraged.