I have been testing HFI on my robot with a VESC6 plus and TP4070 on 12s.
The spinning mass is about 4.5kg so has a good amount of inertia.
When I am controlling it with duty cycle mode I increase the throttle and it starts spinning normally, very smoothly accelerating from 0 speed with no cogging or weirdness.
The ERPM shows the correct direction.
This happens about 9/10 times.
But 1/10 times it starts spinning in the wrong direction, still very smoothly and identical in performance with no cogging or anything, just the direction is wrong.
The ERPM shows that the direction is wrong!
Once the ERPM hits the switchover erpm from HFI to sensorless the motor slams to a halt and starts spinning the correct direction.
Another interesting quirk is if you set the ERPM switchover point quite high then you can run the motor and control it just fine, except its going the wrong way. If you stop the motor and start again it keeps going the same way.
It is also very bad when the ERPM switchover point is too low, it will start to oscillate back and forth.
How do I stop this from happening? Or at least how do I make the vesc at least switch the direction if the ERPM shows the motor is going the wrong way? I don't really understand how the ERPM can show its going the wrong way but the VESC just doesn't give a shit. It's like it picks a direction and stays with it, until you hit the switchover rpm and it goes "OH I am meant to go the other way DERP better slam the motor to a stop instantly and go the other way 
"
Important to note I have had MANY reports of people having this happen, there is actually quite a few posts across the various forums about this, but normally it gets confused with the motor just always going the wrong way and the person is told to switch the wires around. Can we please have an actual discussion as to why this happens and how to solve it. Thanks.
Some videos (The correct way for it to spin is with the teeth spinning towards the camera, looking from the right side it would spin Anti-Clockwise):
Spins the wrong way and even after stopping the motor and starting again keeps going the same way. When the switchover erpm is hit it stops and spins the other way.
Pushing the motor in the wrong direction, third time it starts to go the same wrong direction it was pushed in and accelerates a little before hitting erpm switchover and going the right way.
(The drum is limited to 8% duty cycle in these videos, normally you wouldn't want to be anywhere near it. Also I don't suggest spinning/touching large dangerous spinning things by hand, this was a very cautious demo with the torque reduced to a point where I can stop it by hand)