This is what I get when I enable debug level logging:
{"reqId":"Eo3VvQpvkJZzIFgDW9j2","level":0,"time":"2019-07-14T15:10:38+00:00","remoteAddr":"188.154.221.5","user":"--","app":"core","method":"GET","url":"\/apps\/files\/","message":{"Exception":"OC\\AppFramework\\Middleware\\Security\\Exceptions\\NotLoggedInException","Message":"Current user is not logged in","Code":401,"Trace":[{"file":"\/var\/www\/nextcloud\/lib\/private\/AppFramework\/Middleware\/MiddlewareDispatcher.php","line":95,"function":"beforeController","class":"OC\\AppFramework\\Middleware\\Security\\SecurityMiddleware","type":"->","args":[{"__class__":"OCA\\Files\\Controller\\ViewController"},"index"]},{"file":"\/var\/www\/nextcloud\/lib\/private\/AppFramework\/Http\/Dispatcher.php","line":97,"function":"beforeController","class":"OC\\AppFramework\\Middleware\\MiddlewareDispatcher","type":"->","args":[{"__class__":"OCA\\Files\\Controller\\ViewController"},"index"]},{"file":"\/var\/www\/nextcloud\/lib\/private\/AppFramework\/App.php","line":126,"function":"dispatch","class":"OC\\AppFramework\\Http\\Dispatcher","type":"->","args":[{"__class__":"OCA\\Files\\Controller\\ViewController"},"index"]},{"file":"\/var\/www\/nextcloud\/lib\/private\/AppFramework\/Routing\/RouteActionHandler.php","line":47,"function":"main","class":"OC\\AppFramework\\App","type":"::","args":["ViewController","index",{"__class__":"OC\\AppFramework\\DependencyInjection\\DIContainer"},{"_route":"files.view.index"}]},{"function":"__invoke","class":"OC\\AppFramework\\Routing\\RouteActionHandler","type":"->","args":[{"_route":"files.view.index"}]},{"file":"\/var\/www\/nextcloud\/lib\/private\/Route\/Router.php","line":297,"function":"call_user_func","args":[{"__class__":"OC\\AppFramework\\Routing\\RouteActionHandler"},{"_route":"files.view.index"}]},{"file":"\/var\/www\/nextcloud\/lib\/base.php","line":975,"function":"match","class":"OC\\Route\\Router","type":"->","args":["\/apps\/files\/"]},{"file":"\/var\/www\/nextcloud\/index.php","line":42,"function":"handleRequest","class":"OC","type":"::","args":[]}],"File":"\/var\/www\/nextcloud\/lib\/private\/AppFramework\/Middleware\/Security\/SecurityMiddleware.php","Line":143,"CustomMessage":"--"},"userAgent":"Mozilla\/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/75.0.3770.100 Safari\/537.36","version":"16.0.3.0"}
{"reqId":"6ciOyBpNuu5Icob2A2cw","level":0,"time":"2019-07-14T15:10:39+00:00","remoteAddr":"188.154.221.5","user":"--","app":"cron","method":"GET","url":"\/cron.php","message":"Run OCA\\Files_Sharing\\ExpireSharesJob job with ID 4","userAgent":"Mozilla\/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/75.0.3770.100 Safari\/537.36","version":"16.0.3.0"}
{"reqId":"6ciOyBpNuu5Icob2A2cw","level":0,"time":"2019-07-14T15:10:39+00:00","remoteAddr":"188.154.221.5","user":"--","app":"cron","method":"GET","url":"\/cron.php","message":"Finished OCA\\Files_Sharing\\ExpireSharesJob job with ID 4 in 0 seconds","userAgent":"Mozilla\/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/75.0.3770.100 Safari\/537.36","version":"16.0.3.0"}
It doesn’t return any error in the web interface.
Fedora 30 + nginx, latest Nextcloud release.