It's pretty hard to think of ANY scenario in which the rotors would stop turning in that short a time, even if you wanted them to.
Well, Whirly, I can. Some are now coming round to my earlier suggestion that a possible fenestron problem of some sort
may have occurred and that it
may have precipitated certain actions that could fit the available evidence already on record, including the stopped rotors. It should be remembered (some obviously haven't so far) that there may be tail rotor failures other than a "straightforward" drive failure.
I wrote the word in italics for a reason. For example, the drive and fenestron may remain working, but control of the blade pitch might
not.
A few questions for those suitably qualified on type: What form does the EC135's tail rotor pitch control mechanism take (as in from yaw pedal to the fenestron itself? Is it cable, more than one cable, a push/pull rod, hydraulic or a combination of one or more? Is maximum positive pitch runaway practiced in the EC135 simulator?
More is known about generic helicopter tail rotor drive shaft failures than is known about tail rotor control failures. In-flight diagnosis may be very difficult in the face of confusing and rapidly divergent aircraft behaviour. Simulators may not realistically replicate actual aircraft behaviour, btw, it's known as "off model", where the simulator response is a mere "best guess".