We had a power outage problem yesterday and now, I have noticed that users have problem attaching and uploading files. I did upload a file in a group. the post is sent, but when I click on the attached file, I get

ow_userfiles/plugins/base/attachments/5bcb322edef13_5bcb322ede8d2.pdf

404 not found.

Indeed there is no such file in /var/www/html/ow_userfiles/plugins/base/attachments/

Checking the folder in the server, I see many files which refer to previous days. The permissions are

-rw-r--r--. 1 apache apache    1928 Oct 12 16:29 5bc09aba5b820_5bc09aba5b0ab-100x137.jpg

-rw-rw-rw-. 1 apache apache   40806 Oct 12 16:29 5bc09aba5b820_5bc09aba5b0ab.jpg

-rw-r--r--. 1 apache apache    3212 Oct 13 13:29 5bc1c1b8ae3f7_5bc1c1b8adcc4-100x141.jpg

-rw-rw-rw-. 1 apache apache   68117 Oct 13 13:28 5bc1c1b8ae3f7_5bc1c1b8adcc4.jpg

-rw-rw-rw-. 1 apache apache  227462 Oct 15 09:52 5bc432213c8e9_5bc432213c1ca.pdf

-rw-rw-rw-. 1 apache apache  567468 Oct 17 00:08 5bc64c2fdac77_5bc64c2fda5ee.pdf

-rw-rw-rw-. 1 apache apache   29285 Oct 17 11:26 5bc6eb1a1c869_5bc6eb1a1c131.docx

-rw-rw-rw-. 1 apache apache  593704 Oct 18 18:25 5bc89ec747270_5bc89ec746b71.pdf

-rw-r--r--. 1 apache apache    3556 Oct 18 20:05 5bc8b483645f4_5bc8b48363e28-100x141.jpg

-rw-rw-rw-. 1 apache apache  100645 Oct 18 19:57 5bc8b483645f4_5bc8b48363e28.jpg

-rw-rw-r--. 1 apache apache   20110 Sep 15 13:40 deleted_5b05478c9785a_5b05478a90e3c_5b05478a90b49.p

I think there is a problem with the file system. Maybe it is read only. How can I debug that? Any thought?