I experienced the same thing
After they introduced the throttle on inspects (or server requests) I sometimes experience a lag in switching master. Most of the time everything goes smoothly but once in a while the switch only happends after about 20 seconds, I can usually provoke this by switching master a few times in short bursts.
Forcing the switch to master by using the hotkeys makes no difference, I have even seen the swtich following the toons I switched to in order, so if I switch to toon2, see that the switch is not made and I try to switch back to toon1, perhaps even toon3 I can see that they switch after about 20 secs in that order, so to me it seems that requests is being passed it just gets queued sometwhere
Could it be that the combination of other addons and jamba that causes the server to throttle our requests?