BEAR not saving SKU

When I try to save the SKU number with BEAR bulk editor, the SKU is not saved. After hitting ‘enter’ BEAR shows message ‘Saved’ but after 1 second, it jumps back to the old SKU number.

When I try the same action a second time, the number IS saved correctly.

This happens only with SKU, the other attributes are saved the first time.

Any idea?

I have the newest version installed.