Do not treat the disposer as a way to empty a pan of cooked starch in one load. Follow the permitted waste and feeding limits, and put large leftovers into the appropriate food-waste collection.
What the observation tells you
Softness alone is not a useful measure of drainability. A large wet mass can move through the chamber differently from a few plate scraps and then accumulate in the outlet path. Adding more water is not a safe experiment once drainage has slowed.
A useful next step
If the problem began after a large starchy load, record that detail. Stop using the disposer until the restricted water path has been assessed.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.