Pixelation after export

Hiya, I'm trying to export my video but every time I do it the video comes out looking terrible. The videos and text are really blurry and pixelated. All the content looks fine both in the original video files and in the preview window on premier pro.
My default settings are attached. I have also tried:
Exporting in H.264, QuickTime and H.265; Match source and youtube 1080p preset; use previews on and off; max render quality on/off; making a copy of the project and exporting from the copied file; exporting via the media encoder queue.
Any suggestions on how to sort this out?