A few suggestions…
To eliminate a possible MIDI conflict, make sure you haven't assigned the CC's 30 and 31 to any other knob or parameter.
Assuming there is no conflict, the fact that CC value of 127 only gives 100% feedback and not 110% sounds like a firmware bug to me.
For KB4 and KB5 parameters did you set both MIN VAL and MAX VAL to max Feedback? (This is a long shot, and I'm probably barking up the wrong tree…)
Finally, another long shot, does the LF+ send CC's as 0 to 127 or 1 to 128?
Hope this helps.
