Strange green edges on scaled footage

Hi there guys,

My name is Pierre. New here and unfamiliar with how this works.

I noticed a weird thing today when i scaled some footage (i shoot with a Nikon D750 dslr)

Underneath and on the right there is this strange green edge that appears to be outside of the footage. It never appeared before but now since 10.3 i noticed it.

Anyone else experienced this?

Hope someone has an idea to get rid of it.

Pierre