dekopro cordless drill chuck won't tighten, bit keeps slipping out. how do i fix this?

Incorrect chuck operation causes this.

Procedure:

1. Turn tool off. Disconnect power source (remove battery pack).
2. Hold the inner chuck sleeve (Sleeve A) with one hand to secure it.
3. Grasp the outer sleeve (Sleeve B) with your other hand.
4. Rotate Sleeve B counterclockwise (as viewed from the front) to open jaws.
5. Insert bit fully.
6. Tighten securely by rotating Sleeve A clockwise.

If that didn't work: Inspect the chuck jaws and bit shank for damage or debris. Clean with a dry cloth. A damaged 10mm keyless chuck requires service by a qualified repair person.

Heads up: Always ensure the bit is secure before starting. A loose bit can eject and cause injury.