The preview cleared unconditionally 2s after a committed seek; on a device
still buffering, the live position hasn't caught up yet, so the next key
press re-based off the stale position and re-targeted the same spot -
discarding the seek exactly on the slow hardware the coalescing targets.
Re-arm the clear until the live position is near the target, with a 10s
ceiling backstop (same settle pattern as LiveSeekAccumulator).
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