Unreal Media Texture - purple debug padding line?


I keep having an issue with a purple line appearing in my video (screenshot). I think it might be some debug line showing that the video size does not match the outline but I can’t find any way to turn it off or be able to turn it black or adjust the scale so it would not appear. The video is played through Media Texture. I followed this tutorial how to make it:

[Play a Video File | Unreal Engine Documentation][1]

This is in mobile development environment for Samsung Tab S4, screenshot taken from Tab.