The power grid which is absorbing the generated power is capable of handling plenty more power than the motor and overloads can provide (assuming, of course there isn't a small transformer, wiring, etc which is improperly sized).
The overload relay, fuses/cb/MCP will still protect the motor and wiring whether its motoring or generating.
As the quote above states, the motor would have to be rotating pretty fast before it would cause an overload trip... Say it's a 1750 rpm motor, full load generating would be 1850 rpm. If its rotating at 1900rpm, its ~ 2x fla, so its going to trip.
I, too was sitting back waiting to understand what DB resistors are doing on an induction motor. Perhaps it was a wound-rotor motor originally, and they were used for speed/torque control by adjusting the secondary (rotor) current?
In theory, series resistors could be used with an induction motor to starve the current, so the motor would produce lower torque, and thus speed, but it's uncommon. It was used in some reduced voltage starters way back, but not cost effective, so you'll rarely see it.
I'll bet when you see it in person, the problem will eventually show up as something simple.