When I try a search for NUE-MAR I get
Something went wrong
We didn't find a match. Please choose different search options
Are you searching for NUE-MAR or a multicity search , such as NUE-ZRH , ZRH-MIA and MIA-MAR
If the latter , then I think that the issue is likely due to married sector availability ; that a class is available for A-B and also for A-C when searched for separately, does not mean that it is necessarily available for A-C via B