Model warps upon reversing frames

SuperSparkplug

So, I'm using a character I made in Maya for a Unity game project. I wanted to make a walk backwards animation by simply taking the frames of my walk forward section and reversing them... This has become much harder than anticipated. The first image attached has how the walk animation looked normally. The second one shows what happens every time I reverse the frames

I've tried everything I can think of. I've used the "*=-1" method in the graph editor, I've used the scale tool which almost worked but several of the frames either misaligned within its range or fell out of its range for no good reason. I tried resampling the curve as well. One time it worked but was really choppy, though everytime I've tried it since refuses to work. Any idea what's wrong or how to fix this?

P.S. I know I'm going to get this question but yes, I'm using HumanIK. Yes, I know it's not conventionally supposed to be used for riging and animation without mocap. I was experimenting with it, got to like it, and got pretty far with it despite a few glitches to the point that I REALLY don't want to abandon it for this character as of yet, especially since I'm about 2 - 3 animations away from completing him.

timotronprime

Scale your time from the dope sheet.

Not sure if this will work with HumanIK; never used it.

Vailias

Inverting all those values in the curve editor will break it like that.
Use the dope sheet reverse the frame order not the values.
You'll still need some tweaking, but that will work better.