So, I followed this tutorial to make a digitigrade leg:
An it has worked fine for all the rigs I have made with it. Like this one:
That is, until I opened it in Blender 2.8:
Somehow the leg bones are detaching from each other. It also does a bit of weird jittering when you move the IK bones. It also does this on all the other models with this leg IK that I have opened in blender 2.8. All the other IK constraints work normally. How should I fix this?