I think this bug may still be around. I have one user with ArchiCAD 18-5100 on an iMac 27" with Yosemite 10.10.4. She said it's happened several times, and each palette is still checked in the Window menu. They each have to be turned off and back on again. They appear in the same location, but not necessarily stretched as they were previously. As far as I can tell, it's only happened to one user out of 50.
I'll look around her machine to see if she's got anything odd loaded.
Chuck Kottka
Orcutt Winslow
Phoenix, Arizona, USA
ArchiCAD 25 (since 4.5)
Macbook Pro 15" Touchbar OSX 10.15 Core i7 2.9GHz/16GB RAM/Radeon Pro560 4GB