I had one client replace some worn bearings recently and they installed two floating bearings in a direct coupled overhung fan with a Falk grid coupling.
They realized and corrected their mistake before I was on site again. From their description it was quite evident that something was wrong but given the process, it may have had to run for a while after restart.
What WASN'T evident was the fact that the motor bearing cage was broken by the axial hammering it took when the free-floating fan shaft collided with the fixed motor shaft.
So it required a 2nd unscheduled shutdown after our next regular visit revealed a great big anglefish at cage frequency. (Good catch, Climb!
I've also seen stainless clad shafting lose its cladding and huge screw conveyor pipes break because of two fixed bearings.
So I can add one thing to the discussion:
You almost always need a fixed and floating bearing somewhere. Where should be determined by the designer.