Black borders on side of screen with 720/540p content.

I never noticed this issue before but 720/540p have black borders on the side of screen (1080p and 4K content is still fine). If I change resolution in Kodi to 1080p the borders disappear. I'm using RPi 4 and Libreelec 10 beta 2.

I went back and checked Libreelec 10 beta 1 and its the same.

Then I tested and 9.2.6 and it doesn't have this issue.