Try localize this problem. If the problem is in PSQL driver or Spring dependences. Maybe the problem is in your OS.

Windows with postgres has an issue of localization and drivers: it's sending something through Power Shell or something like that and may turn some symbols into garbage (solved with switching system encoding to UTF-8), but '/' isn't a special symbol, you may get \0 symbol in your string.

Please, write more about your problem. What's your pom.xml (or gradle), about OS... Maybe you have strange getters/setters or ouput, or in your repository interface. Try searching all the path of this object with the field fileName. The problem may be hidding everywhere. Add more System.out.println(fileName); in your @service and getters/setters. If it is cut in first setter problem is not in your code