more multiscreen wierdness

At work I have laptop + external (hdmi) screen. Yesterday I went home, woke laptop from sleep, and had no panel. Previously panel always went with 'primary' display, which was laptop with no external monitor, and external when connected. Which worked fine. I tried logoff/logon, then reboot. Didn't fix it. So I re-added panel, carefully setup as I wanted. Today I connected external monitor. Now each display has it's own panel. Seems like a regression.