the problem- it takes TWO TAPS to switch the state of the H9! whaaa? very weird. One press will activate it, then the next press does nothing, and then the next will bypass it, and the next does nothing, etc.

It sounds as if you are using the switch in toggle mode, so it first sends an ON and next sends an OFF. The ON will toggle the bypass status on the H9, the OFF will do nothing.

I'm not an ES-5 expert, but on looking at the manual, you should be able to set the switch to MOMENTARY mode (set MOD to MOM under ASSIGN) – this should solve the problem.