Hello hello, I'm not familiar with EC traction or Torin machines, but I have spent hours pulling my hair out adjusting a dozen imperial 525 gearless machines with KEB F5 drive and MCE controllers, so maybe I can offer a little insight.

Try a couple easy things first:

- Check encoder mounting. Run the elevator and make sure there is no encoder wobble or otherwise loose mounting.
- Make sure the encoder wire is ran in a separate conduit from the motor wiring.
- Make sure excess encoder wiring is not looped up next to high voltage wiring (I see this a lot in re-mods)
I actually once had a box fan running close to the encoder wiring cause noticeable vibration in the cab while it was running.
- Try to disconnect the loadweigher and run the car.
- See if adding a little weight to the car makes any difference.

Now for the PITA part:

- Make sure you have correct brake spring tension and pick voltage. At least on the imperial machines, too much spring tension can cause the brake to not pick consistently and feel very rough inside the car. Also I tend to have more luck with lower brake pick voltages
- Make sure the brake plunger and sleeve are clean and lubed up (no scoring also) if the Torin machines require it.

Drive:

My only F5 book I have in front of me right now is from 2014, so it's a little old, but most functions should match up.
With Synthetic pretorque you should be able to cleanly pick the brake, and hold the machine long before sending pattern to the motor. It's helpful to initially set brake pick and pattern delay times high with synthetic pretorque and then dial them back to find a good inbetween.
There is a nice write up on synthetic pretorque in section 5.12.4 of the drive book, but I'll summarize below.

- Set LF30 (Control Mode) to 5. This turns on synthesized pretorque
- Set US17 (Pre-Torque timer ramp up) to .2
- Set US18 (Pre-Torque timer ramp down) to .2
- Set brake pick and pattern delay so that the brake picks and you have a solid 1 second or so of the drive holding the machine at zero speed. Run elevator on inspect both directions at the bottom and top of the hoistway. It will probably roll back some, that's ok initially. Take note of the amount of rollback. Increase US17 and or 18 by increments of .2 until little to no rollback occurs. Assuming that helps and the brake picks cleanly before the drive patterns the motor, readjust pick and pattern delay to be less lethargic and you'll probably want to decrease US17 and 18 by a little as well. There are also a couple more drive params - PLF31 and PLF32. I have not had to mess with them though. I think they are used to adjust the strength of the pretorque. You probably won't have to adjust them if your car is balanced.

What is the capacity of the car?
Does it have the R6 Regen unit or is it braking resistors?

If all else fails you could probably give KEB a ring. They are usually pretty helpful with weird drive issues. But it almost sounds like it could just be brake/drive tuning issues. At least my past few experiences bias me in that direction.