On case insensitive filesystem (Windows, OSX), the filename given as argument to the window.open_file API method is used to open the file, which works fine, but is used to set the view.file_name() instead of the actual filename.
This lead to some issues with some external software (like git, but others coming from LINUX too) that is partially case insensitive (AAA.txt is not the same file as aaa.txt for git).
In addition some plugins that use the view.file_name() as key for some internal dictionary are more or less broken.
Could you please check the actual filename when calling window.open_file and use it instead of the one received as argument ?