This is a common problem. The H9 expects a CC value greater than 63 to enable the tuner, but then expects it to go to a low value before it is triggered again. In effect it expects a switch that sends a high value when pressed and a low value when released.

You may be able to persuade your RJM to do this.

But, if not, use Program Change. One send can enable the Tuner, the next can take you back to where you were before. Or, somewhere else.