I have a do it best garage door. Pretty sure it is made by chamberlain. The model number is a 4000. It does not go up or down all the way it all of a sudden started doing this. Have know clue. It has no sensors so thats not the problem as for as things being in the way. Any ideas with this model.

SOURCE: Door will only close when held down

if you obstruct the photo eye does the light flash ?

SOURCE: Chamberlain door will not close, despite down force set to max

Problem solved, sort of-
My unit has self diagnostic capabilities: next to the remote sync red button, is a yellow light the indicates diagnostic readings by blinking. In my case the light was flashing 5 times after the door failed to close. This meant RPM sensor failure. I rechecked the sensor and "flywheel" cap and found that it was not completely secured. With the "flywheel" in the proper position, providing readings for the RPM sensor, the door completely closed.
But my yellow diagnostic light is still flashing 5 times. My door is operating correctly, but the diagnostic feedback is still not completely happy with my RPM sensor. So I will keep and eye on it.

SOURCE: My garage door opener doesnt close all the way.

The motor is probably either stalling because the door is too stiff, or you have a beam break detector that is being triggered when the door is halfway down.

SOURCE: I hae a Chamberlain Whisper

saety beams blocked or out of alignment.

SOURCE: Garage door opener doesnt close the garage

If you have to hold down the button to close the door, you are bypassing the sensors ...
Check the alignment of the sensors. Should see a solid GREEN light