Thanks for asking your question here. If this happened after your software update, you can try wiping the cache partition and check if the sound quality returns to normal. If it didn't, you can try resetting the camera settings on your phone since this only happens when you're recording a video. You can find the step-by-step article on how to reset the camera settings here: https://www.samsung.com/ph/support/mobile-devices/how-to-troubleshoot-camera-app-errors/
If all of this didn't solve your concern, you need to send an error report through Get help > Send Feedback so you can inform our Samsung devs about this issue. You can also follow the steps through this link: https://www.samsung.com/ph/support/mobile-devices/how-to-submit-an-error-on-samsung-members/
Hope these troubleshooting steps can help you resolve your issue. Thank you!