Mercator Sailing: Course and Distance

[Gene222]

I am still hung up on 180 meridian crossings, or maybe not. I ran my program to calculate the course and distance of a 180 degree meridian polar crossing.
Pt1: Lat 80 N, Long 45 E
Pt2: Lat 80 N, Long 135 W
The program gave me a course of 270 deg and a distance of 1875.7814 nm, which does not make any sense to me. I inputted the same coordinates on the starpath.com Mercator Calculator, and it gave a course of 270 deg and a distance of 1875.4003 nm, which also makes no sense to me. After thinking about it, I am beginning to think Mercator Sailing simply can't handle a 180 deg polar crossings. What do you think? If it is not a limitation of Mercator Sailing, I don't think I am interested in fixing this. My program is attached.