Those packets are simply too old. The harm of this congestion generating algorithm can be minimized to a degree by having the transmitter inform the receiver what it's buffer size is. That way, the receiver won't go around asking for packets that the transmitter has already thrown away. The quality of this algorithm depends on the assumptions that its OK for the radio receiver to be 5 or 10 or 20 seconds behind the transmitter. Once a receiver runs out of NACK's, it agrees not to transmit any more.
Transmitters renew receiver's nack quotas from time to time.
On a congested link, the receiver runs out of its quota, and stops sending NACK's. If a transmitter increases nack quotas when it gets fewer NACK's. With this scheme, receivers throttle back on the number of NACK's. A link can snoop a receiver's nack quota, and add it to it's own quota. A link may want to derate its total quota by some factor.