Multicast group message queue

I would like to know if each multicast group has its own queue for downlinking messages, as it is implemented for each device. If so, if a system is composed of 03 gateways and when sending a message via multicast, the network server sends the message to G1 and waits for the TxAck. Upon receiving, it sends the message to the G2 and waits for the TxAck, and the same process is valid for the G3. If G1 is offline, the network server does not receive the TxAck, so it does not send any messages to G2 and G3. And over time, the queue will reach its maximum capacity. Does this description make sense? Is there any solution (workaround) to this issue?