So I had another Mini GS in yesterday. The customer reported an issue where balls were just rolling out the barrel, or it would shoot 1 or 2 shots then back to balls just rolling out.
So with this 1 the 1st thing i noticed was that when pulling the trigger (no air and eyes off) that there wasn't the nice loud ping i would expect to hear.
A nice little test to do it point the marker at the floor and keep pulling the trigger and begin angling the marker towards the sky. If the ping gets quieter the more you point it towards the sky then you have a solenoid issue.
Pull the grip frame off and take the top half of the air transfer tube off, followed by unplugging the solenoid and unscrewing that too.
With the old solenoids you need a decent small pozi drive screw driver. with the new solenoids its a small allen key.
Undo the 3 screws. Pop the top off. Grab the core and pull it out. Give it a wipe down with some kitchen roll and apply a small amount of dow33 lube to the core stem. (not the top or bottom seal faces) core back in the body, (Should slide in nicely). top back on and reassemble. Now hopefully you should get a nice loud ping when firing.
If not then check your battery has more than 9V (a nice new 1 will have around 9.6V).