Something like this can happen when you're changing channels if either your home upload speeds have dropped or if the IR Blaster has been moved away from the IR Sensor of your set top box. A little bit of lag is normal, since the changes have to upload from the streaming device, download to the Slingbox, make the changes through the set top box, upload those changes from the Slingbox and then download them back to the streaming device. I would try running a speed test on speedtest.net and then checking the placement of the IR Blaster to make sure this is still in line with the sensor in the set top box.
I hope this helps!!