Mute won't latch

[QuacksMeUp]

Never experienced this until I moved to PT 8 on an HD system (happens at 2 different studios). Virtually identical setup with Command 8's.

If I press MUTE, the button unlatches the moment I roll record or playback. At other times, if my timeline is somewhere along the track (not zero) when I press mute, it seems to write automation AT THAT POINT for muting... but not preceding that point.

Same thing happened tonight with PAN. I was merely playing with PAN during a playback. But it seemed to write automation.

In all cases, the track was set to READ mode.

My only work around has been to view the track in MUTE (or PAN) mode, select the automation data, and delete it. Then, everything is fine. I can MUTE when and wherever I want; the button stays latched (as it should) without writing automation in Read mode.

I assume I have some preference set that shouldn't be... but I can't identify it.

Any suggestions?

[Howardk]

I am not sure I understand your situation 100%, but it doesn't sound like a preference to me but rather seems like there is simply mute automation data on the track which is toggling the mute. . . There are many ways that can happen, often by copying or moving a region with automation to another track etc. . . I also often see automation way downstream on tracks and no idea what has created it. . . but just delete the automation and all is good after that. . . or if you are recording and in a hurry, just open the automation window and "Suspend" automation and clean up later.