Audio sync on iks

Hello, I'm having a syncing audio issue regarding a iks using beaver bev on cw800.... I have to set up on 2 diff receiver, first iks rocket on charlie file 2.52 conecting usb dongle, no issue with audio, 2 second setup, same setting conecting on beaver with bev this one have sometime on some channel and sometine on other channel have syncing audio issue... The audio is late for about a 2 or 3 seconds.... I tried reset many time, restore and everyting..... Someone have and idea to resolve it? Thanks a lot for your time....