kicked: Packet Flooding: Player Tick

Recently, we have been experiencing an issue where multiple players are disconnected with the error `kicked: Packet Flooding: Player Tick` during the spawning or despawning of Deepsea elements, and we are trying to identify the cause.

We have excluded custom NPCs from Deepsea and have reduced settings—such as the number of islands spawned by the Deepsea option plugin—to values lower than the defaults.
Do you have any ideas as to what might be causing this?
The server currently has plenty of headroom regarding specs and resources.
Normal FPS ranges from 145 to 200, so performance is quite high.

"Content": {
"Islands": {
"Count": 5,
"Spacing Size (bigger = more spread out)": 300.0,
"Edge Buffer (bigger = further from outer edge)": 750.0,
"Minimum Spacing (hard minimum distance)": 600.0
},
"Ghost Ships": {
"Count": 3,
"Spacing Size (bigger = more spread out)": 80.0,
"Edge Buffer (bigger = further from outer edge)": 450.0,
"Minimum Spacing (hard minimum distance)": 400.0
},
"RHIB Groups": {
"Count": 3,
"Spacing Size (bigger = more spread out)": 10.0,
"Edge Buffer (bigger = further from outer edge)": 1150.0,
"Minimum Spacing (hard minimum distance)": 300.0
},