garage door not closing fully?

Have an up and over garage door that sticks when trying to close it. Also looks like one of the wires is looser than the other one and when the door comes down on the groove attached to the frame the hook on the end of the wire, one side, sticks into one of the cut outs in the groove and prevents the door closing fully? How do I sort this, and can it be done by DIY or do I need to call in the pros? Door is a Garador (RGI)