Risked this in the evening. Decided to try less leaf (I usually do a heaping teaspoon, but went with a flat one) and to be more exact about the 8 oz water recommended per teaspoon on the sachet. I then added about 2 oz (this I eyeballed at about 1/4 of what was currently in the cup) of the latte mixture.
Success! Once again, actually paying attention to things produces results! It’s amazing how often that works.
I am also somewhat weirded out because this is basically a tea that I don’t want to drink without milk or milk like thing (fear my double negative!), where usually I am against milk in my tea at all!