Wireless missed ACKs (critical)
The number of missed ACKs (acknowledgements) exceeds the threshold set in Expert Thresholds. Whenever an 802.11 frame is transmitted, the transmitting station expects the receiving station to return an ACK, otherwise it retransmits the frame.
Possible reasons for the event:
Two or more stations transmitting simultaneously and causing collisions
The receiving station or AP is out of range
The receiving station or AP is down or there is some other problem with the device (e.g., failing hardware or misconfigured software.
Any one of these results causes both devices to back off and retransmit at random times.