It is not lagging. i'm looking in the launcher as minecraft is running, it is NOT skipping any ticks. everything in minecraft works perfectly fine, except for that scoreboard error. fact is that command blocks are not working the same as they were 2-3 weeks ago during 16w06. and that will break quite a few thing. many poeple have been working on maps during the snapshot stage so they can release them in 1.9. but if this keeps up there will be lots of version switching just to make a custom map work for whoever is playing it.
Confirmed by me as well.