I think (but I’m in no means an expert here) that the implementation (in NVDA) might not match the spec here. These are the attributes that made NVDA properly announce autocompletion. The error message doesn’t say which attribute it has a problem with, but I suspect it’s aria-expanded, and if I remember correctly removing that caused NVDA to misbehave. If someone more familiar with this stuff wants to weigh in here that’d be very welcome.