That's even weirder. How can there be significantly different values for a fundamental measurement? Tiny fractions of a degree are one thing, but 2 degrees? I guess the two airports aren't going to have automated landings so a couple of degrees isn't a problem, but this seems like purposeful misinformation in comparison.
Anyway, if the the values they are using are from the same source as yours, then rounding to the nearest 0.1 degree would set them to 270.
That still loops around to why the software to having a problem. The reverse approaches are 0 degrees true, and 0 is just as problematic for trigonometry as 180 is. I can see where the opposite problem would be more likely to exist - a database of the lat/long coordinates for each end and a failure to determine the correct arctangent, but the ones I looked at aren't exactly 270 so the arctangent should not be infinite nor zero.
Puzzling.