Hi.
Please see here: [1.5.0-1.5.x] File name too long
If you change the parameter it will not have an effect for existing files. You need to either fix long file names in advance or (what I would recommend) set up a new and empty vault with the needed filenameLengthLimit and then migrate your files into that new vault.
Please note: this limit is for filenames. It does not include the path. Magenta is limiting to the path, including the filename. Further more this is a local configuration. If you put a file into your vault via android, the specified filename limitation will not apply.