When the Teleport window is opened, it slides any open chat windows into Local. This obscures the pulldown handle on Local, so its length can no longer be adjusted manually. Closing Teleport doesn't restore the proper layout, but closing/reopening the affected chat windows does.
The issue is present both in the bitmap- and in the GPU-render client.
Opened a help case for it already, but reporting it here just in case others run into the issue and don't know what's going on. :)