To reproduce:
1. Open attached project (resize test.zip)
2. Open "resizetest" scene
3. Open the Game window
4. Resize the Game window

Expected behavior: image should scale normally
Actual behavior: stretched view of the original image (see gif)

Note: the bug happens when you have two cameras with an image effect that create a new render texture and blit it on the destination in OnRenderImage(source, destination)

Not reproducible with: 5.1.4p1, 5.2.4p1, 5.4.0b1
Reproducible with: 5.3.1f1, 5.3.1p2