Modulation on H90 delay algorithms don’t necessarily work in a serial fashion like this where you can envision two delays hooked into a modulation pedal in series. The modulation in the delay algorithms affect each one of the dual engines simultaneously and often times because each voice tends to be auto-panned to each output for the widest image possible, you don’t end up with the results you’d get if you just used two simple delays in series with each other.

You may want to experiment taking the Delay Mix parameter of an algorithm and setting it to either A or B, but not up the middle. This forces either Delay A or B of that algorithm to function in mono. Route that to a delay algorithm with built-in modulation and see if that works better for you.