Suddenly, when I use Delete to remove a section of a track I get Delete and Move instead. Can anyone tell me how to get back to a simple Delete again?

I'm using Logic Pro X on an iMac with a 10.8.5.6 OS. 3.4 GHz Intel Core i7; 8GB 1333MHz DDR3

After years of using Logic without this problem, the program has started to do a Delete and Move when I select Delete from the Edit menu or press the Delete key, and after all the obvious kinds of trouble shooting, I haven't been able to do a simple Delete again. Can anyone help?