Hey , I am using Blender 2.90.1 and I will try to explain a little more clearly the problem. I can't remember about using "keep offsets" but I am pretty sure I did. I usually animate from the Side View and also use the Front and Top views as helper views. The rigged character is perpendicular(90deg) to the Side,Front and Top views.
Here is a step by step .
- I animate the walk of the character straight forward. Everything works perfect, IK Targets for feet work great.
- I used an NLA clip for the walk forward and also add Path Constraint.
- New NLA clip, I then animate the figure turning 110deg to the left. I start animating the figure moving forward at 110deg from step #1 above.
- I try to change the 3d view so I am looking at my character as close as possible to planar side view so I can rotate the bones properly.
- After doing this I notice the IK bones acting a little strange .
- After doing a few more steps the IK bones become very erratic.
I will try again from scratch to find out more about this issue. I also have another character rig(Mike_Rig) I downloaded from the web that I can test with to see if this shows up with it. I just find it easier to animate with my rig which is why I used my rig.