Futaba failsafe??
I'd suggest the BATTERY FAILSAFE was activated. Your description of what transpired is a mirror of what should happen with battery failsafe.
What was the voltage of the battery? Under load? New battery? NiCD? Cell count? Did you charge it? Have you cycled the battery and or measured the capacity? Did it happen while you were using several control surfaces or under level flight conditions?
Definitely loose the metal to metal clevis! However this would not cause the problem you describe, if anything it would implement a control surface lock-out/failsafe (last known setting or pre-programmed failsafe settings).