If you drink the potion while standing in front of the gate on the Isle of Wonder, the gate disappears. Attaching screenshot, but don't have recent save before drinking the potion.
version 1.2.0svn52089
Windows 7 x64
King's Quest VI CD/Windows/English
mingw x64 build
screenshot
I can confirm that this was also present in the original interpreter.
Updating the description and lowering priority then
save game
Moving to the wiki, known SCI bugs page:
http://wiki.scummvm.org/index.php/SCI/Bugs
We are finally patching the relevant script to fix this.
It wasn't specific to that room. It would happen in every room that uses AddToPics-elements.
Fixed by a4f08654b3529ce3a257ddcbef24cc6ea2edc709