It might be that they're not failing more frequently, just differently.
The direct drive type usually suffer vane failure, making the rotor hard / impossible to turn or the seal fails and they leak fluid out the spindle. I don't think we've had a magnetic drive pump fail in that manner, they all seem to die because the drive magnet has broken up.
With the older (direct drive) members of the fleet being retired one by one, it might be that we're seeing more magnetic failures because they are now the majority of what we have.