There have been frequent server crashes for a week or so with a crash report that always points to a nullpointer exception for Ticking Block Entity. Yes I know the stack trace shows no issues with anything besides HashMaps class and the actual Minecraft package, but Mojang won't address the issue as it's not vanilla. The following crash report shows the issue caused by a furnace, other reports have been for hoppers, at least one was simply  Description: Exception ticking world
 The following link is for one of the crash reports:
 https://gist.github.com/blarosen95/f2072d8413d1dba4b0525bc86ce4db55

Edit: Here is another crash report that I was aware of but had to wait for a full copy of in order to post it on here: https://gist.github.com/blarosen95/c6884f95b00ebedb722812c00532d769