Sinusoidal PWM generation on Arduino with a simulink Model has a frequency issue. How to fix it?????

I'm building a sine wave inverter. I want to use arduino uno to generate sinusoidal PWM pulses. I've made a model on simulink which produces exact pulses that I need but when I deploy it on hardware, output frequency of the pulses almost diminishes(0.2-0.5 Hz). Pin 5 and 6 on arduino uno give 980 Hz pulses and I'm using 980 Hz carrier frequency. My output in software looks like

But my output has same wave shape but with a frequency of almost 0.3 Hz. While in software, carrier frequency is 50 Hz and pulses have a frequency of 980 Hz. Can anyone please tell me what's going on and how to fix it.

[Emmanuel Elendu]

I am having same issue can someone help