Hi
Blockly 1.3.4
I think servo-motor-backward-right and servo-motor-backward-left blocks are exchanged.
Could you check them please?

Here is the code for forward-right and backward-right. I think the second one is wrong:
servopos SMA_pin, SMA_forward : servopos SMB_pin, SMB_stop
servopos SMA_pin, SMA_stop : servopos SMB_pin, SMB_back