Big lags spikes on my server



I’m running a pixelmon server and I have a major problem : with 15/20 players online, my server have sometimes big lags spikes which cause a freeze during 10 seconds, however I set my render-distance at 5 and rised the chunk unload delay in the main config, here is my timings :
Is there a way to resolve them ? As you can see, this is caused by ticking and chunk unload…
Thanks ! :wink: