This must relate to the markers, it is hard to see but it looks like there are some large marker errors.
Did the model finish parameter optimization and are foot markers placed correctly?
I observed that the xiphod marker is strangely placed far below where it was during the laboratory trial. Also the centre of pressure and markers of the left foot appears to be outside the foot.
It looks to me like the foot markers has been allowed to be optimized too much, and then they have found a location "outside" the foot.
I think you need to look at the markerprotocol and turn off the optimization of some of the foot markers.
It seems to happens only on Left side so compare the left/right optimization settings (OptX,OptY OptZ) for these markers that you have these symmetric. Notice the Green/Red arrows in the model when you are doing marker tracking.
I have turned off the optimization of the foot markers. I also included a weak driver for the hip and ankle. The foot still penetrates but the markers look better
Thank you for your response. I have tried to make the adjustments based on your suggestion. It still penetrates the force plate.
I tried to also look up past posts on this forum to see if someone else have similar challenge but couldn't find any.
Is there anyone having similar problems and what other steps was taken to fix it. Though the results wasn't affected, I don't feel fulfilled knowing that there is a problem somewhere in my work.
I look forward to hearing from you and other who might have suggestions.
I read my previous answer again and realized i should have suggested to move the marker downwards and not up. Moving it down should have the desired effect, sorry for this.