Recently 3G infrastructure has been deployed at the customer site. Before this deployment 2.4 band was working fine (no consecutive ping drops/ high delay). After 3G deployment customer is experiencing high ping drops/delays on 2.4 band.
Moreover customer has informed me that whenever they shutdown the 3G infrastructure everything will be going working smooth as soon they power on the 3G infrastructure 2.4 band users are experiencing ping drops and high latency
Exactly the same as you mentioned, the ap's are almost 5 to 10 feet away from the Cellular devices.
Looking forward.