TYPO3 Core

The LanguageController of the lang sysext causes Exceptions thrown by the PropertyMapper.

I get an error when trying to call the updateTranslation action:
Exception while property mapping at property path "":Could not find a suitable type converter for "mixed" because no such class or interface exists

There are (at least) 3 "mixed" parameter type annotations in action methods.

When I change the parameter type annotation of the $locales parameter of the updateTranslation to "string" it works, but I'm not sure if there are other method calls passing an array as $locales