Wander - if the PFCs fail they revert to manual - the controls are heavy but the ac is perfectly controllable. But, IIRC, as long as the engine is windmilling the hydraulic pump will be developing pressure and the controls will remain powered unless an excessive load is placed upon them.
From the video, there is no obvious indication of an engine malfunction - but it can not be entirely discounted, especially a partial compressor failure where the engine keeps running but develops significantly less thrust.
That said - Andrewn, I'm not sure what you are referring to; I can see no evidence of mechanical failure, etc.