When Gordon Freeman attempts to use Kleiner's teleporter, Lamarr jumps from a vent and damages it while Gordon's teleport is in progress, which forces Gordon to proceed on foot once the malfunction subsides.
When Gordon Freeman attempts to use Dr. Kleiner's teleporter, Lamarr jumps from a vent and damages it while Gordon's teleport is in progress, teleporting him all over the city, including Dr. Breen's office in the Citadel. This forces Gordon to proceed on foot once the malfunction subsides.