Hi all,
From the shower (hot side ,cold side and diverter on tub spout) I would turn on the hot and cold sides,and within a second or two water would dribble/flow weakly out of the shower head before the diverter in the tub spout was pulled up to shower mode. These things i did check if helps: All piping is 1/2" copper from shower valve to shower head, 48" from shower head to hot and cold assembly/valves. Could it possibly be the plastic diverter valve inside the tub spout? Any