print failed at the end

hi everyone, 

I am disgusted, the print failed just at the end.

after about 7hours of printing.

is anybody knows why?

Not a guarantee, but I'm guessing loose set screws. Might be the ones on motor shaft. It may have shifted giving it nothing to print on top of. That would be where I would start.

ok thanks kyle, I will look after printing which is in progress.

where is the motor shaft?? is it where the filament is extruded?? ( sorry i don't speak english very well )

The motors that turn the belts. Back left and right.