I'm posting this since I have seen others with this problem but haven't seen a solution or work around mentioned.
Since an earlier version of 6.x I've been unable to use the Pause or Speed Limit buttons. They would not stay activated longer than about 30 seconds before auto-magically turning off. Today I disabled the Scheduler since I don't use it. I assume the Scheduler is enabled by default since I've never used it before but it was enabled. The Pause and Speed Limiter buttons now appear to function as expected.