I have a mare who is similar. Ex lesson horse (aka green horse they put kids on until they finally gave up on sending kids to the hospital..) so she either way under reacts or way over reacts at the same time. So quiet ask, no response, harder ask no response, make and she gets all worked up, then next quiet cue she overreacts. She's gotten much better (though she hasn't been ridden recently) but I did a LOT of voice cues as it wasn't something she was programmed to tune out, it really helped her get over that. Not completely relevant to the OP, but it's interesting what you find works sometimes!