The lock shoe grooves may have burrs or dirt.

Replace the lock shoes. Clean the grooves. Refer to Steering Column Jacket - Disassemble - Off Vehicle and Steering Column Jacket - Assemble - Off Vehicle .

The lock shoe spring is weak or broken.

Replace the spring. Refer to Tilt Spring - Disassemble - Off Vehicle and Tilt Spring - Assemble - Off Vehicle .

The lock shoe is seized on the pivot pin.

Replace both lock shoes. Refer to Steering Column Jacket - Disassemble - Off Vehicle and Steering Column Jacket - Assemble - Off Vehicle .