Quick answer: Unity Cinemachine virtual camera priority changes ignored during an active blend? The brain locks the blend pair until completion - call Brain.ActiveBlend.Complete() to interrupt.
Higher-priority camera enters during a 2s blend. Brain finishes the existing blend before considering the new camera.
Complete the active blend
brain.ActiveBlend?.Complete();Forces the brain to re-evaluate priorities. New camera takes over on the next frame.
Or use Live Camera override
Set ManualUpdate mode briefly; pick the new camera; restore. Bypasses the blend lock.
Configure blend curve
Use a faster blend curve for the priority-change case. Doesn't fix the interruption issue but reduces latency.
“Cinemachine blends are atomic transactions. Mid-blend overrides require explicit interruption.”
If you change camera priorities at runtime, document the blend-interrupt pattern. New engineers will discover the lock the hard way otherwise.