I just got a digital tachometer to check the speed of my motors on my P3A. The motors are the 2312A type. I have had a few accidents. I have suspected slower motors for some time now. One motor appears to be slower than all the rest. I hear a noise when hovering which seems to be coming from a motor and sound like it could be a bearing. So, I tested my motors speed while idling to confirm if it is good or bad. Now I need your help. I'm using a SainSonic TA-3 Digital Tachometer. Results looking from the front to the back of the drone battery in the back: Front Left: 2061 RPM Front Right: 2248 RPM Back Left: 2948 RPM Back Right: 1865 RPM It appears the Back right at 1865 is much slower. The back left may be normal as it is the only one with the higher speed? The front left, front right, and back right may need replacement. Maybe I should replace all motors. Sure could use your advice and help. Thanks.