This behavior and the thread called EIP Tick Wait can be produced due to the "TimerTickInterval" property of an Ethernet/IP session. This value gets/sets the tick interval for stack operations. Since this interval is set to 1 ms by default, the RT controller will try to execute all Ethernet/IP-related tasks as fast as possible, resulting in high CPU usage. To solve the issue, you can increase the interval between the timer ticks to reduce CPU usage. This property can be changed through a property node in LabVIEW, as shown in the image below. (Note: "TimerTickPreemption" must also be set to FALSE).
Make sure the "TimerTickInterval" is less than your fastest UDP otherwise you may experience connection issues. A good rule of thumb is at least half of the fastest UDP's period.