Different contractions in hamstrings with EMS at same levels?

I have a compex sport 400 and have used it for a few cycles.

I also have a recurring ankle sprain on my right side that has affected my leg and how I use it in sport from the hip down.

I cannot get the same intensity contraction with new pads placed the same on both my hamstrings. My right side needs more current to get a contraction and the contraction still isn’t the same. Less of an instant twitch from the short compex ramp time vs. the left side and a different feeling during sustained contraction.

Does this point to an underlying firing problem with that hamstring that I should attempt to resolve? And if so would it best be done in the weight room, with more EMS, or through soft tissue work?