Agents use to system file watchers to be notified of files updates. The error message appears for Synchronization jobs and is frequent for a Linux OS, especially if there are lot of files and subdirectories in the synced folder. If the agent process hits the system's limit of watchers, the Agent won't be notified about file update and thus the only way for it to learn about these is by rescanning the folder, either manually or periodically. It's better to increase the watchers limit.
By default, system allocates 8192 watchers. Run the command to check that and see the output
This number can be increased by editing
Either append the line using any text editor:
... or run command in terminal
sudo sysctl fs.inotify.max_user_watches=XXXXX
where XXXXX is the number of watchers you'd like to set. Do not set amount of watchers more than 2147483647.
Restart the agent.
Error code SE_FS_TOO_MANY_SUBSCRIPTIONS