X3e Prod x64, Windows 8.1 x64, Akai MPD26 Preset = Generic 20
Set up MPD26 transport buttons via Controller/Surface Properties as:
<< = Start/Stop Rewind
>> = Start/Stop Fast Forward
STOP = Stop With Now Marker
PLAY = Play/Pause
REC = Record
Everything works as expected with the exception of one case; press << and let run until it stops itself at the beginning of the project. Clicking the toolbar >> now continues running instead of stopping when the mouse button is released. Clicking << will get it to change directions, but it will continue until it reaches the beginning again no matter what is clicked. << and >> continue operating this way until << on the MPD26 is pressed.
It appears that there is some missing logic in Sonar. I believe if << is pressed, the action should be programmatically toggled off if allowed to stop on it's own at the beginning of the project, also handling the case where << is pressed when the transport is already at the beginning.
This is 100% repeatable with the MPD26. I have not yet tried with a different controller.