Question Changing FOV seems to distort decals

So I've introduced a targetgroup that I follow. In following this target group cinemachine adjusts the FOV accordingly as it goes and this seem to have exposed some issues decals and FOV.

Previously I had a static camera with FOV 20 and it worked fine like this:



If I change the FOV to 15 like below, the blood decal should still look exactly the same as above, but it's all distorted (almost like certain parts have been moved and also certain parts have been chopped off):



Also as you change the FOV to different values it distorts in different ways.

Any idea why the blood decal appears differently merely from editing the FOV value?

Any advice much appreciated. Thanks.