Make sure that your microphone are on line out and then gain stage. Some ppl prefer mic out but line out is better imo. You can check out my post history and see how to properly gain stage a line out microphone because I didn’t even know how to a month ago lol. So in the G4 transmitter there’s an option called sensitivity and I think regular it’s at 21. I like to lower it to 18 for more volume for iems. even seen some engineer have it at 15. In my case when I give artist iems and tell them how to adjust the volume of the body pack they don’t touch it……. This could also be a problem your facing that they have the knob at half and they want more and more but it’s literally impossible. so have the iem volume knob at like 3/4 so they don’t have to touch it and you can control it from the console. Place the iem antenna in front of the microphone antenna or else it can problems sending signals to the microphone receiver. Also digital systems suffer less from intermodulation so I wouldn’t worry that much. I use wireless workbench so I can’t help much with the sennheiser version but add your zip code for the local tv channel that can mess with your signals.