When using the editor, creators might accidentally hit the playtest key when placing objects: since the action of clicking is used by both normal mode and playtest mode, this causes a race condition where the editor switches to playtest mode (EditorUI->0x1A4->0x3AC) before the action of placing the object occurs. The state of the editor is then inconsistent, because it thinks we're constantly placing an object, and we cannot place more.
The fix is very simple: we check for the user click action, and we prevent the editor from entering playtest mode if the action is not done (for experts: if ccTouchEnded() is not done yet).
Huge thanks to night, who has asked me to fix this bug in the first place, and who told me a consistent way of reproducing it!