I am running Spigot 1.9.2 and every block under the standard size of a block glitches when you walk on it. Once your on it it's so hard to get off so you have to /spawn. I have tried it with different versions of Spigot 1.9 and it still does it ITS BACK! I've found out it's non Ops that get stuck
So is there a permission for it? Because i run a server with normal players and i don´t wanna give everyone OP, just that they can walk over slabs...
This was a while back, it was a plugin that was causing it but I forgot what one, if you could send a list of your plugins I might be able to remember
I had the same problem and i tested all my plugins and found that NoCheatPlus is the problem, then i removed it and it was Fine.