Hmmm ... interesting. I had found that the figure (I "inherited" a rig) had a smoothscaley channel in the left toes for the foot, and a smoothscalez channel in the right toes for the foot. So I created a smoothscale channel (z and y) for each toe.

Bingo, this problem appeared.

 

So that appears to be the answer.

 

I've never really used smoothscale channels, so this is definitely a learning process.