Scanning through some old project code:
#define ADC_VREF 1.249f
Uhh... that seems odd. *looks at data sheet*
1.240 V nominal.
My first guess was typo, but I recall the developer who wrote this and they are *exactly* the sort of person who'd put a multimeter on a dev board and go "YEP IT'S A 1.249 V PART". I'm being uncharitable but this isn't the first mess I've had to clean up this month.