En la pagina del fabricante aparece que por lo visto el receptor tiene dos modos de funcionamiento PPM, por lo visto esos movimientos erraticos de los servos en el modo FASST Multi se corregirina cambiando el modo PPM del receptor,a ver si lo pruebo mañana y os comento.
Go here :
http://www.frsky-rc.com/ShowProducts.asp?id=39 Its possible to switch between too PPM mode !! frsky explain also for the jitter and failsafe
1.TF Receivers Please note that there are many differences between some brand and FrSky, especially in binding procedure and failsafe setting. Read the instruction manual carefully and set up devices as described below.
1.1 Compatibility:
FASST 2.4G System (TM7, TM8, TM10, TM14, etc.)
FrSky TF Module (TF-8M, TF-14M)
1.2 Specifications:
Number of channel: 8
Operating Voltage Range: 4V~10V
Dimension: 53mm*30mm*11mm
Weight: 13.5g
Latency: 14ms (FS)
7ms (HS)
2.Setup
2.1 Bind procedure:
Turn on the transmitter, connect the battery to the receiver while pressing receiver’s F/S button. After the RED LED is off and GREEN LED is solid, the binding process is completed and working mode is activated.
2.2 Setting failsafe:
TF series receivers support failsafe function for all channels. Please kindly follow the steps below to set failsafe:
1) Bind the receiver first, and disable failsafe on the transmitter side;
2) Set failsafe at any required position on any channel;
3) Press briefly the F/S button of the receiver, the GREEN LED of the receiver will flash twice, indicating the failsafe is set up successfully.
If you do not need the failsafe function any more, just re-bind the receiver to set default failsafe mode.
Warning: Due to different failsafe settings between transmitter and FrSky TFR8, users must disable
failsafe on the transmitter side. Otherwise you will notice a jitter during a period of time on the channel you set failsafe.
2.3 LED status: 
3. How to switch between two PPM modes
Turn the transmitter off, connect the battery to the receiver, press the F/S button of receiver for 6 seconds and then release. The red LED will flash fast in HS Mode and slow in FS Mode.
