Suspect it is network issue and the packets are dropped.
Ping AP from AC with 1450 bytes, we find no packets dropped.
Ping AP from AC with 1500 bytes, there are some packets dropped.
It is MTU issue, one of the devices between AC and AP dropped the packets with 1500 size. After we changed the interface MTU from 1450 to 1500, it is working fine.
When the ping from AC to AP with 1500 size is successful the issue is resolved