So managed to sort it by messing with the x5 modes:
Line5x format
Selects the output format of line5x.
1920×1080: 1080-line output, which crops a few active lines from top and bottom of incoming video signal. [default]
1600×1200: 1200-line output that displays all active lines of incoming video signal.
1920×1200: 1200-line output that displays all active lines of incoming video signal.
Also found the bleed is caused by my Bandbridge scart switcher.
The OSSC is sick. What an amazing piece of gadgetry.