How to Adjust a Miter Saw
Miter saws often need their bevel angles and miter angles adjusted, and this article explains generalized steps to make these adjustments on most miter saws.
Power Tool Care and Maintenance 101
This article suggests guidelines for power tool care and maintenance. It also describes information tools available at eReplacementParts.com.
Discussion
Discussion for the Makita LS1216L 12" Dual Slide Compound Miter Saw
The brake on your mitersaw is an electric brake. When you release the power switch, the switch sends current to a brake coil in the motor's field. This reverses polarity to the motor and stops the armature from spinning. Good contact from the motor brushes is also important for this to work correctly.
The most common issues with a mitersaw brake are the brushes, part number,CB-154 , and the switch part number, 650618-3. It is less common but a damaged field can also make the brake not work correctly. It is part number 596356-2.