Sir
Try pulling the horizontal deflection board down out of its' sleeve and make sure the small board mounted on it is firmly seated on its' pins. Then make sure the horizontal board itself is firmly seated, you may need to add a shim of a few millimeters thickness between the sleeve cap and the bottom of the board, to hold it against gravity. The horizontal board is mounted upright between the green and blue CRTs and has red/blue/white yoke wires plugged into it.