I assume this was supposed to be a running sequence/cycle. It feels out very much out of balance, like a rolling shutter for motion suits., with the effect that the character could fall backwards any second, hence my question.
My impression is that fixing the one foot will not help, nor would this be the right action to do. The Pelvis should be one of the most central parts, so both feet will slide in the same way. Then the whole rig is moved forward and the sliding is equalized with the forward movement. To fix anything else seems wrong to me.
I would think that there are two main delivery formats, one is walking on the spot and one is just walking. To showcase this, I have placed both here:
The left one would be then, if used in an Animation Clip, looped and set to “relative” so an loop means just a continues walk. The one on the right would be in need of a Pivot object, to move at all.
Perhaps have a look here what a “typical” sliding foot looks like.
Note that moving the Animation clip back will always need an adjustment for the pivot Object.
The Pivot (or any parent object) that would be needed to fix the example above [movie clip] would have to oscillate back and fore for each cycle. Then saved again and adjusted for minor slides.
If you are working with this suit currently, just use any camera (even a position locked iPhone is fine) to get some footage from the real movement, so you can place that behind the rig and adjust with certainty.
In case you just got this from an unrelated 3rd party, perhaps switch the source to Maximo or something that works.
All the best