Sometimes when you dig for worms there is a possibility that your character gets stuck immediately after starting to dig. The circle will disappear and you will be unable to move until you wiggle with your character. Then you will be able to move again.

This has been up already for a longer time, so it’s no issue which came up with the latest patches.

It appears randomly, so it’s not reproducable as you want. But if you try often enough it should appear sometimes.