I had a long reply composed this morning, then … {poof} Crash! I came to the same conclusions that you ultimately did. The LFO sweep ‘freezes’ at 0.00Hz. You often get more exacting, repeatable results by using direct entry into H9 Control’s parameter value boxes.
It seems like the corner / center frequency increases with increasing MOD DEPTH. Might be cool to utilize those dead spaces between FILTER TYPES to change the corner frequency for LOWPASS / BANDPASS / HIPASS.
