I believe the tail twitching come from two areas. The first is simple. Raise the esc feature that allows an insensitive motor cutoff.In a couple of cases the tail twiching was related and caused by very quick momentary ESC controlled motor shut downs. (8 hours to find that one) The second is more difficult and the 401 appears to be the most prone. Static electricity generated by the belt in the tail drive system. After all if you look at a static electricty generator whalla! you have a tail rotor drive system. The carbon framed version appear the most sensitive. The following in order of effectiveness has help me eliminate the twiching.

1. Spray lube the belt with a graphite lube. I use Lock Ease. Also use the same on the bearings.
2. Spray drop coat the model with Static Guard.
3. Ground the tail boom to the main frame using a small wire.
4. Form a light weight 4 sided metal shielding box and mount the 401 inside of it. 3 sides and a bottom

If your issues appear better this time of the year it is because the static is less due to the higher humidity. Here in Michigan this is a wild problem in the winter months. Thanks, Dave [email protected]