Thats how is is suppose you works it can only scale in integer positions I.e 1x,2x,3x
you should take a look at this https://www.scirra.com/tutorials/73/sup ... sizes#h2a3
have you tried just using letterbox Scale as that wont shouldn't deform and works just like letterbox integer scale but will scale and # like 1.2, 2.5, 3.2321 if need to fill the screen as much as it can while maintaining aspect ratio?
for the manual
Letterbox integer scale mode is identical to Letterbox scale mode, preserving the aspect ratio, but it also only zooms to an integer scale. For example it will only scale at 1x, 2x, 3x, 4x etc. and never at something like 2.5x. This is important for games using Point sampling (usually retro style) to preserve exact pixel-perfect accuracy when scaling the game. This also means black bars can appear at both the sides and top and bottom.