Media texture resizing problem

How do I correctly resize a media texture I’m using as a tv screen, it was working fine in 4.12.5, but in 4.15 it’s gone to pot!

It’s a 480p texture, looks fine on a 200x200 bsp but won’t resize on a 50x50, I’ve tried rescaling u and v coords to 0.25 each, it’s not working, I’ve also tried using the align fit option in geometry to no avail!

Can someone please help!