Description of the Safety Problem While converting the Doona infant car seat from vehicle mode to stroller mode, the wheel deployment mechanism caused the harness straps to tighten automatically and forcefully around the infant. When the caregiver activated the wheel-deployment handle after removing the seat from the vehicle, the harness tension increased suddenly without any adjustment being made to the harness. The infant immediately screamed, and visible bruising was later observed consistent with excessive strap compression. At no point was the harness adjuster intentionally tightened by the caregiver. The tightening occurred solely during stroller wheel deployment. Injury Details The infant sustained visible bruising in areas consistent with harness compression. Medical evaluation is being pursued. The incident caused acute distress to the infant. Suspected Cause / Design Concern The car seat was received second-hand. It is suspected that the soft goods (padding) may have been removed for cleaning by a prior owner and reinstalled incorrectly, allowing the harness webbing to be routed over a moving component of the wheel deployment mechanism rather than under it. However, removing and reinstalling padding is a foreseeable and expected user action. A child restraint system should not allow a foreseeable reassembly error to result in automatic tightening of the harness during normal operation. The wheel deployment mechanism should be mechanically isolated from the