@Orisar I think the interference is coming from your other deco units.

  @Orisar 

Have you tried the Network optimization tool in the deco app? You can find the tool under the More tab (bottom right) > Advanced > Network Optimization

When you optimize the network on the Deco APP, it sorts of restarts the Wi-Fi module of Deco once to re-detect the nearby wireless condition and decide whether or not to switch to other wireless channels.

A similar effect could be obtained using the reboot schedule.You could set the schedule to reboot once a day which will force the decos to see if they need to switch to a different wireless channel.