check the potentiometer voltage when pressing the pedal in reverse.

the 1A contactor does not activate until the voltage reaches 0.5v.
make sure it achieves this voltage in both forward and reverse.

you may have some resistance in the reverse control circuit that is keeping it from achieving it's required voltage to allow 1A to pull in.

a simple adjustment to the C/A setting may help this out, it should be set to 9, if not then adjust it to 9.

the rapid tune up settings are as follows
creep: 7
C/A: 9
C/L: 6 (this is set at factory and should not need adj)
1A time: 7
1A DO: 3
Plug: 5
FWPU: --
FWDO: --