Some MIDI controllers, such as some touch-sensitive motorized faders, can send complex MIDI messages. The control may be sending a MIDI message when it is first touched or moved and another message when the control is released. Live may not assign the control correctly because it is learning the last MIDI message that it receives. Below is a solution for controls that have this behavior:

Turn on MIDI Map Mode in Live.
Select the parameter you want to control.
Touch and hold the control on the MIDI device.
Turn off MIDI Map Mode.
Release the control on the MIDI device.