the technique used by wiringPi to emulate PWM is based entirely on software and isn't very reliable. The code can be seen here
. This type of code doesn't work very well from user-space on multi-tasking operating systems like Linux. pigpio uses a very different technique based largely on DMA hardware and delivers much better results. For example, with pigpio it's possible to emulate PWM and to control LEDs and servos without flicker and jitter.