I recently bought a shower diverter kit for my shower, American Standard 2 handle job. Installed it with no leaks, but water drizzles out the shower head when the spout is on and the diverter knob is still in the down position. Is this problem in the spout with the knob? What can be done to fix this?

I recently bought a shower diverter kit for my shower, American Standard 2 handle job. Installed it with no leaks, but water drizzles out the shower head when the spout is on and the diverter knob is still in the down position. Is this problem in the spout with the knob? What can be done to fix this?
As a rule several things can cause this situation. 1) Too short a shower raiser.
2) excessive house pressure and 3) some crud got in the spout and is setting up a back pressure that forces some of the water back up the raiser. Since cit worked before we can eliminate the shower raiser, What's the house pressure? Is it excessively high? If you haven't got a pressure gage,(see image) that connects to the hose bib then purchase one and check the house pressure..
Try removing the diverter spout and turn the water back on. Does the shower head still leak? Let me know, Tom