Tips for using wireless headphones without interference

We now have 4 sets of wireless headphones, 2 Sonys and 2 Sennheisers. Each brand has three distinct channels, and the 3 for Sony are different from the 3 for Sennheiser. We currently have both Sonys in E1 and both Sennheisers in E2. We just had some problems in E1 with not being able to pick up one of the tables. I'm not sure what was going on, but I fixed it by changing the channel on the headphone base from the middle to the right. It seems like it's a good idea to have the two headphones on the left and the right, rather than in the middle, to decrease the chance of interference. Other things we discovered today is that if a channel is staticky, it will automatically switch to a different channel, like an automatic radio tuner. If you don't know this is happening, it can be confusing why you keep picking up someone else's table no matter how many times you change the channel. We're still having problems with static that we don't know how to fix.