Thanks Walter – I am thinking its the third dot point as I dont pre-comp anything, so there cant be an issue there
I need to figure out what kind of layer style I’ve applied now (I have no idea what it could be, so Ill need to go over them all with a fine tooth comb)
I ended up exporting the screen composition as a video with alpha, and then replacing that composition layer in the main composition with the video file. Luckily no resolution quality issues!