Stephane,
Welcome to the group.
First check that the clear plastic block in the tape reader is not loose. If it is tie the two ears that rest on the black rod down with small cable ties.
Check that all the contact wires are in the slots of the corresponding vertical reader pins.
Whatever you do dont spray any contact cleaner into the contact block. Some cleaners will designate the plastic.
The control handle (FREE/STOP/START) Should not move easily. Check that the spring that holds the detent block is not broken.
Get back to me if none of these fixes dont help.
73,
Wayne
KB1FDW