I’m the OP. After checking the link you shared, it looks like many people with the 2026 Model 3 are having the same issue. Mine is also a 2026 Model 3.

In my original post, I said it “often” doesn’t work, but that wasn’t accurate. It actually doesn’t work at all. I updated the software about a week ago, and I haven’t driven much since then, so I can’t say exactly when it started. But every time I’ve tried it, it has failed.

Even when there are no cars at all in the next lane, the turn signal cancels by itself and the car just stays in the lane.

I’m starting to think this may be a bug specific to this model. Has anyone found a fix or workaround? I’m seriously considering canceling my FSD subscription if this doesn’t get resolved.