Deadlock when running JBoss Tools Project Validator on startup

The workspace is one EAR project, a couple dozen EJBs, 2 WARs, a couple dozen JAR webfragments (deployed inside the WARs), some misc projects - 67 projects alltogether.
When opening it sometimes locks up completely - UI is not responding, process CPU is at 0%.
Here's what it looks like:
This time I just opened the Problems view and clicked Markers, which never opened. But I don't think this isn't necessary, pretty sure it sometimes hangs without clicking anything at all.
It always shows JBoss Tools Project Validator in the Progress view when this happens.
VisualVM reports a deadlock, seems to be JBoss Tools Validator related: threaddump-1518088511239.tdump
I think this used to happen with JBDS10 too, but I don't know for sure, because I don't have the threaddumps.