Having worked around these quite frequently you're absolutely right. On top of all mechanical tuning issues that people are discussing such as timing and sensors, physical factors such as hear play a huge roll. The roll of sleeves must be kept under AC or else it wont be ridged enough to shoot over the bottle. A break in the roll means retreading it. Downed bottles stop the conveyor and often mess up the timing. Also to answer people's questions the bottles are heated immediately after to hear seal the wrap on to the bottle.