I have modified the jetty options increasing the acceptors , etc
My jetty now looks like this:
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<jetty_options>
<acceptors>4</acceptors>
<acceptQueueSize>4</acceptQueueSize>
<lowResourcesMaxIdleTime>2</lowResourcesMaxIdleTime>
</jetty_options>
The linux carte slaves are working perfectly with the default values.
Let's see how it goes