I have a weird issue, some user can see some thread in the recently updated

if they search for it they can find it but if they open the node, that thread is not visible.
Only certain thread and only certain users.
Anyone can point me on the right direction?
Hosted in a VPS with Ubuntu and MariaDB Ver 15.1 Distrib 10.11.14-MariaDB

if they search for it they can find it but if they open the node, that thread is not visible.
Only certain thread and only certain users.
Anyone can point me on the right direction?
Hosted in a VPS with Ubuntu and MariaDB Ver 15.1 Distrib 10.11.14-MariaDB