High CPU usage and lots of exceptions in log

IntelliJ consumes around 30% CPU on my 8 core machine. I thought that was a little excessive so I looked into the log and saw a lot of "java.lang.AssertionError: Stub and PSI element type mismatch in StringsKt.class: stub , AST MODIFIER_LIST; Element(MODIFIER_LIST)". I tried invalidating the cache and restarting. Didn't help. Any ideas?

Configuration:

IntelliJ IDEA 2016.2.4  Build #IC-162.2032.8
JDK: 1.8.0_112-release
VM: OpenJDK 64-Bit Server VM
OS: Linux

Full log is in: https://pastebin.com/csZtzeSn