Sharing file and Internal server error

Hello, community. Today I have one trouble with my oC. We create a folder with some docs and share it via Link. In one moment users view a message "Internal Server Error, please ask your IT-admin". I found that this message vanished when I`m again loging by the user account which create shared folder. This situation repeat a few times. How can I resolve this problem?
I try to found log files, but I can't

Your webserver error-logfile should contain more information about internal server errors. In Linux it is often in /var/log/apache2/... or simliar paths.