Don't know if this will help you, but at some point the same thing happened with me. What happened here was the Lab switched to Relative mode instead of Absolute. You can switch that either on the Lab itself (it's under Setup -> Global), or via the MIDI Control Center but do note: There's a bug in the MIDI Control Center, so if you want the Lab to behave in Absolute mode, you actually have to have MIDI Control Center to tell it to behave in Relative mode.
Hope this made sense and helped.... I love the thing but hate the poor instructions and documentation, especially re: MIDI Control Center. Also hate that it doesn't work properly in Ableton Live.