Whether Tesla was Serbian or Croatian is one of the most controversial topics on Wikipedia[1]. As is typical for Wikipedia he has been added and removed from the list of famous Croats a number of time[2]. I don't think that can be classed as a factual error

[1] http://en.wikipedia.org/wiki/Wikipedia:List_of_controversial...

[2] http://en.wikipedia.org/wiki/Talk:List_of_Croats#Tesla