Sometimes the mix can get behind siding or behind gutters and continue to seep out even after you have rinsed. Especially if you apply too much in one area with a good amount of pressure. I would suggest keeping distance while applying or fanning out your spray so there is less pressure and concentration of mix and an even coat applied. This might help eliminate it getting behind siding and falling out after rinsing… If that is the issue here.
This link might help
