If you are having trouble with the Tonic Pad Player turning on and then not turning off, you'll want to check out the "Scale Parameter". This issue appears to be a MainStage bug tied to a particular type of Scale Parameter setting for the on button mappings. For a minority of users the Scale Parameter is being slightly altered to what should be a perfectly fine function (stepped) but it causes the mouse to not toggle off for whatever reason.
To fix this, you'll want to:
- Go to MainStage at the concert level and click the Tonic On button once.
- Locate the "Latch" mapping in the inspector and click on it to view.
- Ensure that the "Scale Parameter" for that mapping is a diagonal line as in the picture (if it's not, click the box as in the second picture to set it to that).