Spontaneus throttle with Mechjeb and joystick

I run KSP on OSX and often fly with my joystick. However, if I have my joystick connected, the throttle will be set to 50% always when I click on any MJ text field to bring it into focus. Clicking different text fields within the same pane doesn't cause this if the pane is already in focus. This will often mess up my trajectories if I'm not careful enough to disable throttle in some way before clicking. Pressing 'X' won't help since the input will go to the text field in question, thus I will need to quickly twitch the throttle on my joystick to reset throttle.