Generally there is only one reason for chlorine lock - Cyanuric acid levels over 100ppm.
Maintain your Cyanuric Acid level at 40-50ppm. Cyanuric Acid is generally known as Stabilizer.
The quickest and easiest way to solve this issue is draining the pool in the same method as you would for high TDS, 12 inches at a time, testing each time, until you reach the desired CA level or between 40-50ppm.
If you do not control the reduction of the CA then be prepared for your pool to "turn". Without the chlorine able to act as a sanitizer your pool will suffer quickly with algae blooms.