Do you want to display a message "You got stuck, game will place player in a free position"? This is no adequate solution I think.

When this happens rarely you could easily place invisible blocks in tricky corners so that the player can't even get there.

I will try to find a solution tonight and post it tomorrow if possible.

EDIT:
My try would be store the last 3 positions of the player and set it back until I can trace again in all directions.