Many thanks for all the help on this one ...
Initially, I had a problem with the 'factory reset' because I was using the Massoth PC-software which does not have a 'factory reset' option. If anyone knows how to do the reset using this software it would be really useful!
Anyway I have now installed the LGB (V6) software which does have the 'factory reset' option ...
For info, these are the values that are currently set on the decoder (directional lighting CV values look okay)
1,4,1-127,Loco Address (standard short)
2,0,1-255,Starting Voltage (in Speed Step 1)
3,3,1-255,Acceleration time
4,3,1-255,Braking time
5,255,1-255,Top Speed
7,23,--,Software Version
8,123,123,Manufacturer ID: Massoth
9,0,0-3,Motor Frequency
13,0,0-3,Function Outputs in Analog Mode (On if value set)
17,192,128-10239,Long Loco Address (High Byte)
18,128,128-10239,Long Loco Address (Low Byte)
29,4,Bits,Configuration Table NMRA (see documentation)
49,5,1-32,F1: Dimming Value (PWM)
50,5,1-32,Light: Dimming Value (PWM)
51,1,Bits,F1: Command Allocation (see documentation)
52,128,Bits,Front Light: Command Allocation (see documentation)
53,64,Bits,Rear Light: Command Allocation (see documentation)
54,50,Bits,LGB Confiuration (see documentation)
56,5,1-32,F2: Voltage (Smoke Generator)
57,1,Bits,F2: Command Allocation (see documentation)
58,0,0-255,Pause Time for Stop and Reversing
60,48,1-255,Back EMF Adjustment Factor
61,0,1-255,Back EMF Adjustment Speed
62,255,1-255,Back EMF Adjustment Strength