Openers manufactured after 1993 have an infrared safety eye system to reverse the garage door if anything is in the way of the door when closing. Sometimes something is blocking the “light beam” such as a broom handle or spider web. It is possible for the sensors to become misaligned and that will also cause the door to reverse immediately or in some cases when they are just slightly out of adjustment the door may travel part way before reversing. Check sensors for an obstruction or see if the lighted indicators located on both the sending and receiving eyes are both lit. If one is out or blinking then they may need re-aligned.