rpd west unable to pick up survivor

ZTMachine

was playing on rpd west as nemisis and had just downed a survivor with basic attack, they got downed in this corner I was unable to pick them up until they moved roughly a minute later they got idk what its called but the little burst of speed thing you get after being downed yea they were put there with that from just outside the doorway on the right if its important the build and addons i was useing at the time are licker tongue and marvins blood