I have also been seeing a similar performance issue, and have run the .php script on all ports but this has not fixed.
Would this be down to Libre, or to the devices/network?
that’s usually performance issue with the device or could be LibreNMS.
Run discovery debug on that device see if you getting any timeouts.
Also, run through the performance docs…
https://docs.librenms.org/#Support/Performance/2