When our tub plumbing was new about 7 years ago, the shower diverter would disengage and pop back up by itself when the water was turned off.
For some time now, it needs to be pulled up by hand to make the water come out of the spout again.

From what I've been reading here, the standard procedure is to replace the entire spout, but these are Grohe Seabury satin nickel finish fixtures ($$$$) and pulling up the little knob sure seems like a real viable alternative to the expense and effort of replacing the entire spout.

Is there no maintenance that can be done to free up the diverter?