I've discovered this just because I created a flow that searches for files in Box by referring to them by path, based on a list of filenames to search in a separate XML file, and sometimes there is not a 100% correspondence between the filename in the XML list and the actual filename in the folder.
Most of the times only the file extention is all uppercase in the XML and not in the actual file, or viceversa.
Since I don't have a way to tell which one is right or wrong, I've found no other more practical solution than trying the action first with all uppercase, and if it fails to try again with lowercase.
In this case it would have been useful to have the option to turn case sensitivity on or off (maybe with "off" by default) on these actions.