The airways data in the sim is buggy at several places.
I have implemented the airways in our GTN750 GPS and we can see some trouble with airway waypoints (reported by many users).
I give here an example but there are many of them. This is an issue at the sim's level.
I think there is some kind of blend with waypoints from different airways with the same name in the world.
The example is the following:
Waypoint TETAN in south Africa and airway UZ2.
The correct airway waypoints are TETAN, AXOPA, EGTIL, UNRAG, APRAX, TEVA, NIBEX.
But the sim gives us PORPI, ISKAB, SLI, TETAN, AXOPA, EGTIL, UNRAG.
The bad waypoints PORPI, ISKAB and SLI are taken from the UZ2 (same name) airway in Brazil.
Correct waypoints as displayed in LNM.
Bad waypoints as given by the sim:
Hope this example will help to fix the issue soon.