Strange Loop Playback Scenario -- PT11 HD

In the past (PT10 and earlier) I've been able to select a region, place PT in loop playback mode and PT will loop that section infinitely, regardless of what other actions I'm taking in terms of adding/removing realtime plugins. Since moving to PT11, I've noticed that while PT is looping, if I add a plugin, PT jumps ahead on the timeline and out of the selected loop range. To get the section to loop again, I've got to stop and restart playback. Then, if I add another plugin, same behavior again.
Anybody know if I've somehow changed a setting in switching from PT10 to PT11? Or is this a new bug?