The boom has lost its position and cannot raise fully, believing it is already at its maximum.

Move the boom to the absolute bottom. Check that the position is zeroed (0 or +1) automatically when it stops at the bottom.

If not zeroed, continue to hold the boom down-button until you receive a question.

Press “Yes” on the question.

This is also a part of the homing process.

Click here for a video tutorial of the above