MBP, OSX Mojave, when using an external monitor with the laptop screen closed everything is cool, unplug the laptop and use built in screen everything is cool.

Once I plug the laptop back into the external monitor with the lid closed AI will snap off screen someplace.

If I use the mission control gesture (swipe up with 3 fingers) the window appears and I can drag it to another desktop, but then it assumes the same position off screen on the new desktop.

The only workaround I have found is to unplug the monitor, resize the window and then plug back in.

I haven't seen this behavior with any other app.