When I tried it, the only unexpected disengagement was on the highway, but it just slowed and stayed in lane giving me lots of time to take over.

Thinking about it afterwards, possible reasons include

• I had cars on both sides, blocking me in. Perhaps it decided that was risky or it occluded vision, or perhaps one moved toward me and there was no room to avoid
• it was a little over a mile from my exit. Perhaps it decided it had no way to switch lanes while being blocked in