can't move random pieces

Not the best jigsaw puzzle game that BFG has to offer in their store.
Good parts: beautiful pictures, different types and choose your puzzle size.
Yuk pars: the worst is some pieces suddenly refuse to move - you can R or L click , move pieces around them, but all you is get is a drafting line drawn.

I've noticed that if the piece is where it should be on the screen, it locks. You then get the drafting line.

In two consecutive puzzles I've encountered pieces that will not move. When I click on "sort" those pieces will move with all the others, but it will not move when I click on the individual piece. I have chosen the option that makes the pieces stick to the board, so the correctly placed pieces will not move when I click on them. But this is not the case with the pieces that refuse to move when I click on them. They may be in the puzzle area or outside the puzzle area--that seems to make no difference. I like this game, but in two out of three puzzles I've played some pieces stick in place when they should not. Is there a fix for this?