Clearly means that a part of your toplogy has a performance issue
.
Locate the devices in a diagram of your topology and see how the trafffic from the lms server should get to that part of the network and via which way it returns.
Check if the path has bad links by checking the interfaces for drop's, crc's, etc.
The time at which you receive an alert probably is the time when link or a device is charged more usual, (backup running)?
Cheers,
Michel