If you press a button that has been bound to the Record function and the record runs for about 1/2 a second then stops and resets the loop, you are not using a properly programmed Sustainable Trigger.
The Record function has Long Press behavior, if you press and hold the button bound to the Record function longer than 1/2 second, it will execute the Reset function. To prevent this from happening you must use a trigger that sends a message both when the button is pressed and when it is released. Usually this means that your footswitch must be programmed to send MIDI notes or MIDI continuous controller messages on both the up and down transitions. If your MIDI footswitch sends a MIDI Note On message when it is pressed but does not send a MIDI Note Off message when it is released, Mobius will think the button is being held down and will reset the loop."
http://www.circularlabs.com/doc/v2/starting.htm#Record%20Stops%20Suddenly