Conflict between simultaneous use servo.h and PWM output on Mega2560 development board

[hzc1111]

I ran into a problem when using it on the Mega 2560 development board: I used pins 12 and 13 to drive two servos, which was no problem, but the motors that were driven by other PWM pins did not work.
According to the official website, there is no conflict with PWM output on Mega 2560. Can anyone tell me why?

[hzc1111]

To be precise, pins 44, 45, and 46 used as PWM outputs were disturbed. As for the other pins, I did not test.
Later, I solved the problem by changing a library, but I still don’t understand the problem.