Error in LOG: Could not create folder

^{“reqId”:“0IdFQiFKvd8v7miFOBEZ”,“level”:3,“time”:“03.05.2021 21:03:46”,“remoteAddr”:“xxx.xxx.xxx.xxx”,
“user”:“user”,“app”:“index”,“method”:“GET”,“url”:"/index.php/core/preview.png?file=Chiemgau%20Br
andes%20Mai%202021/21-05-02%2011-25-10%201149.jpg&x=1024.0&y=1024.0&a=1&mode=cover",“message”:{“Exc
eption”:“OCP\Files\NotPermittedException”,“Message”:“Could not create folder”,“Code”:0,“Trace”:[{
“file”:"/var/www/nextcloud/lib/private/Files/AppData/AppData.php",“line”:157,“function”:“newFolder”
,“class”:“OC\Files\Node\Folder”,“type”:"->",“args”:[“0/2/3/5/3/4/2/114603”]},{“file”:"/var/www/n
extcloud/lib/private/Preview/Storage/Root.php",“line”:75,“function”:“newFolder”,“class”:“OC\Files
\AppData\AppData”,“type”:"->",“args”:[“0/2/3/5/3/4/2/114603”]},{“file”:"/var/www/nextcloud/lib/pri
vate/Preview/Generator.php",“line”:471,“function”:“newFolder”,“class”:“OC\Preview\Storage\Root”,“type”:"->",“args”:[“114603”]},{“file”:"/var/www/nextcloud/lib/private/Preview/Generator.php",“line”:132,“function”:“getPreviewFolder”,“class”:“OC\Preview\Generator”,“type”:"->",“args”:[{“class”:“OC\Files\Node\File”}]},{“file”:"/var/www/nextcloud/lib/private/Preview/Generator.php",“line”:109,“function”:“generatePreviews”,“class”:“OC\Preview\Generator”,“type”:"->",“args”:[{“class”:“OC\Files\Node\File”},[{“width”:1024,“height”:1024,“crop”:false,“mode”:“cover”}],“image/jpeg”]},{“file”:"/var/www/nextcloud/lib/private/PreviewManager.php",“line”:190,“function”:“getPreview”,“class”:“OC\Preview\Generator”,“type”:"->",“args”:[{“class”:“OC\Files\Node\File”},1024,1024,false,“cover”,null]},{“file”:"/var/www/nextcloud/core/Controller/PreviewController.php",“line”:170,“function”:“getPreview”,“class”:“OC\PreviewManager”,“type”:"->",“args”:[{“class”:“OC\Files\Node\File”},1024,1024,false,“cover”]},{“file”:"/var/www/nextcloud/core/Controller/PreviewController.php",“line”:107,“function”:“fetchPreview”,“class”:“OC\Core\Controller\PreviewController”,“type”:"->",“args”:[{“class”:“OC\Files\Node\File”},1024,1024,true,true,“cover”]},{“file”:"/var/www/nextcloud/lib/private/AppFramework/Http/Dispatcher.php",“line”:218,“function”:“getPreview”,“class”:“OC\Core\Controller\PreviewController”,“type”:"->",“args”:[“Chiemgau Brandes Mai 2021/21-05-02 11-25-10 1149.jpg”,1024,1024,true,true,“cover”]},{“file”:"/var/www/nextcloud/lib/private/AppFramework/Http/Dispatcher.php",“line”:127,“function”:“executeController”,“class”:“OC\AppFramework\Http\Dispatcher”,“type”:"->",“args”:[{“class”:“OC\Core\Controller\PreviewController”},“getPreview”]},{“file”:"/var/www/nextcloud/lib/private/AppFramework/App.php",“line”:157,“function”:“dispatch”,“class”:“OC\AppFramework\Http\Dispatcher”,“type”:"->",“args”:[{“class”:“OC\Core\Controller\PreviewController”},“getPreview”]},{“file”:"/var/www/nextcloud/lib/private/Route/Router.php",“line”:302,“function”:“main”,“class”:“OC\AppFramework\App”,“type”:"::",“args”:[“OC\Core\Controller\PreviewController”,“getPreview”,{“class”:“OC\AppFramework\DependencyInjection\DIContainer”},{"_route":“core.Preview.getPreview”}]},{“file”:"/var/www/nextcloud/lib/base.php",“line”:993,“function”:“match”,“class”:“OC\Route\Router”,“type”:"->",“args”:["/core/preview.png"]},{“file”:"/var/www/nextcloud/index.php",“line”:37,“function”:“handleRequest”,“class”:“OC”,“type”:"::",“args”:}],“File”:"/var/www/nextcloud/lib/private/Files/Node/Folder.php",“Line”:176,“CustomMessage”:"–"},“userAgent”:“Mozilla/5.0 (iOS) Nextcloud-iOS/3.4.2”,“version”:“21.0.1.1”}

Nextcloud version (eg, 20.0.5): 21.0.1.1
Operating system and version (eg, Ubuntu 20.04): DEBIAN 10 (buster)
Apache or nginx version (eg, Apache 2.4.25): Apache/2.4.38 (Debian)
PHP version (eg, 7.4): 7.3