Constant errors appearing in log concerning invalid characters

[giovi321]

I constantly get the following error for some files. This prevents the files from syncing with the iOS app Notes for ownCloud (I receive HTTP500 error). I normally delete the file and copy-paste the text in a new file.

ownCloud 9.1.6 (stable)
Notes app 2.0.2

Exception: {"Exception":"OCP\Files\InvalidPathException","Message":"File name contains at least one invalid character","Code":0,"Trace":"#0 /var/www/owncloud/lib/private/Files/View.php(761): OC\Files\View->verifyPath('/giovi/files/No...', 'Musica\r.txt')\n#1 /var/www/owncloud/lib/private/Files/Node/File.php(149): OC\Files\View->rename('/giovi/files/No...', '/giovi/files/No...')\n#2 /var/www/owncloud/apps/notes/service/notesservice.php(148): OC\Files\Node\File->move('/giovi/files/No...')\n#3 /var/www/owncloud/apps/notes/controller/notesapicontroller.php(139): OCA\Notes\Service\NotesService->update(97707, 'Musica\r\n=======...', 'giovi')\n#4 /var/www/owncloud/apps/notes/controller/errors.php(31): OCA\Notes\Controller\NotesApiController->OCA\Notes\Controller\{closure}()\n#5 /var/www/owncloud/apps/notes/controller/notesapicontroller.php(141): OCA\Notes\Controller\NotesApiController->respond(Object(Closure))\n#6 [internal function]: OCA\Notes\Controller\NotesApiController->update(97707, 'Musica\r\n=======...', NULL)\n#7 /var/www/owncloud/lib/private/AppFramework/Http/Dispatcher.php(159): call_user_func_array(Array, Array)\n#8 /var/www/owncloud/lib/private/AppFramework/Http/Dispatcher.php(89): OC\AppFramework\Http\Dispatcher->executeController(Object(OCA\Notes\Controller\NotesApiController), 'update')\n#9 /var/www/owncloud/lib/private/AppFramework/App.php(99): OC\AppFramework\Http\Dispatcher->dispatch(Object(OCA\Notes\Controller\NotesApiController), 'update')\n#10 /var/www/owncloud/lib/private/AppFramework/Routing/RouteActionHandler.php(46): OC\AppFramework\App::main('NotesApiControl...', 'update', Object(OC\AppFramework\DependencyInjection\DIContainer), Array)\n#11 [internal function]: OC\AppFramework\Routing\RouteActionHandler->__invoke(Array)\n#12 /var/www/owncloud/lib/private/Route/Router.php(280): call_user_func(Object(OC\AppFramework\Routing\RouteActionHandler), Array)\n#13 /var/www/owncloud/lib/base.php(891): OC\Route\Router->match('/apps/notes/api...')\n#14 /var/www/owncloud/index.php(54): OC::handleRequest()\n#15 {main}","File":"/var/www/owncloud/lib/private/Files/View.php","Line":1836}