What's wrong with my switch mode power supply circuit?
Since 0.8 is the reference voltage, I'd look closely at R3/R4. R3 have the wrong value (much too small or shorted by a solder bridge), or R4 may be wrong (much too large or cold solder joint).

Also, the feedback resistors on the +12 side are not correct. As shown, they should produce about a 5 volt output