These VFDs have an infuriating number of poorly documented settings.
Here are some that may have gotten you in trouble.
PD002 Set to 0 should allow speed control from the front of the VFD
Set to 1 should control speed from analog input, as scaled
by other PD parameters, and limited by still others. These
limits are why you get the 119.9 lower speed limit. It is likely
that the scaled speed request evaluates to something less
but the limit kicks it up to 119.9
PD070 Analog input - set to 0 for a range of 0-10 VDC
PD072 Higher Analog Frequency - set to integer frequency, in your case 400
If this is set to 60 Hz then the scaled evaluation cannot exceed
60 Hz and the lower limit will kick in resulting in 119.9 Hz
PD073 Lower Analog Frequency - set to 0 This affects how speed is computed
internally to the VFD, but it is not what actually prevents low
speed operation, the limit does that