There are two traits called Stargazer in the Pathfinder data sets.
1) "Stargazer (Varisian)" race trait from Humans of Golarion
2) "Stargazer" campaign trait from Iron Gods Player's Guide
Both use "KEY:Trait ~ Stargazer" and so only one is accessible
I'll change the key for the Iron Gods version.
Unfortunately we can't use the migrate.lst file here to keep this compatible, because it would affect both traits, so this will be an incompatible change, but there is no way to avoid this as far as I can see.