Converting +/- 10 V sine to 0...3.3 V sine
There is a hidden error of negative common-mode voltage on Vin due to the bipolar input. 

A simple solution is to pull both Vin+/Vin- up with 220k To 3.3V  or the equivalent circuit to make Vcm increase within the Rail to Rail limits with some margin. (0.4V)







simulate this circuit &ndash; Schematic created using CircuitLab