I've been doing some tests on our community server after updating to 1.3.1, due to clients complaining of massive amounts of block lag. The server hardware and connection isn't the issue, and the clients machines aren't either. I began taking plugins out and disabling features one by one, and something stuck out like a sore thumb. Orebfuscator. Since removing it, the lag has disappeared completely. I then put it back in and asked clients for feedback, and the lag had returned. Due to the high number of servers who use this plugin, I thought I'd post this to warn you. Try taking it out, and ask your players for feedback. Maybe this fix will work for you! Hope this helped.