I've seen this happen several times. It's an old bug. The below YouTube video has a good example, but there are many other configurations that create this problem.
https://www.youtube.com/watch?v=yKovD5VPUe4
One obvious way to debug is just to run a bunch of random checks across random points on the map, ensuring that A-can-shoot-B = B-can-shoot-A in all cases.
https://www.youtube.com/watch?v=yKovD5VPUe4
One obvious way to debug is just to run a bunch of random checks across random points on the map, ensuring that A-can-shoot-B = B-can-shoot-A in all cases.