Hello @WastaTariq 

Thank you for contacting the Canvas Community. We're sorry to hear you've been experiencing issues with playing audio in videos. As long as after rewinding  or fast forwarding, you are in play mode - it should continue playing audio as it did before you moved the timer and play setting.  It is likely your internet browser and we recommend clearing the cache and cookies or trying another browser.

In Chrome
On your computer, open Chrome.
At the top right, click the three dots 
Click settings and then Clear browsing data.
At the top, choose a time range. To delete everything, select All time. I suggest at least 4 weeks 
Next to "Cookies and other site data" and "Cached images and files," check the boxes.
Click Clear data.

If you are using the Canvas app currently we also recommend doing the same thing:

https://community.canvaslms.com/t5/Canvas-Student-iOS-Guide/What-Student-app-options-can-I-manage-fr... 

If you still have issues, it may be your network or  device  directly. You should contact your school IT help desk or you could speak with canvas support, but if it is indeed an  actual device/network issue there's not a lot they will be able to do for you:

https://community.canvaslms.com/t5/Canvas-Basics-Guide/How-do-I-contact-Canvas-Support/ta-p/389767