Hi,

Since several days I have at least once Jenkins UI that doesn't reply. Background jobs are ok but we have a white screen or nothing from the web UI. We have many (maven) jobs and a lot of plugins. Master have several executors. I can give you many more details if required.
I created a thread dump : https://gist.github.com/aheritier/8593910
You can see "Handling GET" threads blocked with something like :

   java.lang.Thread.State: BLOCKED (on object monitor)
	at hudson.maven.MavenModuleSetBuild.getResult(MavenModuleSetBuild.java:211)
	- waiting to lock <0x00000006ef034588> (a java.lang.Object)
	at hudson.plugins.projectstats.NumBuildsStats.compute(NumBuildsStats.java:52)
	at hudson.plugins.projectstats.column.NumBuildsColumn.getStats(NumBuildsColumn.java:53)

In my screens I'm using the dashboard plugin with various statistics from our builds and it seems that it has some difficulties to compute them.
I'm using the LTS 1.532.1 and I just deployed the 1.532.2 RC but it doesn't help. I didn't notice this problem just after a plugin update thus I don't have a real clue about what to do.