Having hundred and hundred of serialized requests on my server and I have a few warnings like thoses.
I could understand those on parallel request.
Let us say I have 1% of my request raising this warning

Category: org.ametys.site.CacheAccessManager
Message: The lock on page etudiants/fr/international.html was queried to be unlocked by the thread http-8097-2 without it being the owner.
Location: org.ametys.site.CacheAccessManager.unlock(CacheAccessManager.java:195)
Thrown:
java.lang.IllegalMonitorStateException
at java.util.concurrent.locks.ReentrantLock$Sync.tryRelease(ReentrantLock.java:155)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.release(AbstractQueuedSynchronizer.java:1260)
at java.util.concurrent.locks.ReentrantLock.unlock(ReentrantLock.java:460)
at org.ametys.site.CacheAccessManager.unlock(CacheAccessManager.java:185)
at org.ametys.site.GeneratePageAction.act(GeneratePageAction.java:179)