Just noticed. I updated the “Plugin AU Main Type” Value in Xcode, saved in Projucer, and built in Xcode, to remove this plist Error problem, but the problem resides. What happens, it seems that the updated Info.plist will not be copied to the plugin-location. I had to delete the whole plugin from the ~/Library/Audio/Plugin/components, to force Xcode to copy the updated Info.plist.
Maybe the plugin-should be completed remove from the location, with every Xcode build?