The first thing you need to do is to check if the battery power is too low, cause the low power may get you into wireless dropouts.
If the battery is , then the problem is likely caused by the interaction with other wireless mics in your setup.
Pay close attention to any meters or lights on your receiver and try to ascertain what happens to them when the dropout occurs. If your wireless has a 'ready' light, then does the 'ready' light go off or red? If your receiver has an RF level indicator, does this meter fall when the dropout occurs? If 'Yes,' then the dropout is related to the RF signal. If 'No,' then the dropout is only related to the audio (check for a faulty lapel mic, headset mic or cable).
Click the frequency button to assign a new frequency for your problem mic. If the wireless mic performs well on the new frequency, the problem might be caused by an outside source.
Try your transmitter with a different receiver to determine if the transmitter or receiver is faulty.(for example, when using TONOR TW-820, you can match the transmitter to another receiver)
If you're using remote antennas, make sure the antennas are in the same room as the microphone and can be seen by the person holding the mic. When antennas are in a separate room, the wall would weaken the signal; therefore, we would recommend you to keep antennas as close as possible for the best result.
As a rule, antenna distribution is required when using multiple wireless mics (4 or more) to avoid several antennas hanging around, which can compromise signal reception. Proper antenna distribution and placement will help to avoid objects such as wireless receivers, rack hardware (metal), and people (water) - all of which can reflect the RF signal causing dropouts.
Assuming you have antenna distribution and possibly remote antennas, we need to reduce the number of variables and troubleshoot this area. To do this, remove the problem channel receiver from the antenna distribution. Then, take that one receiver out of the rack, put the stock antennas directly on the back of it, and place the receiver 6 to 10 feet away from the rest of your equipment.
We want to isolate the wireless mic and run it as simply as possible. If the mic works fine, then you know the transmitter, receiver, and frequency are in working order. Subsequently, the problem must be with the antenna distribution, remote antenna, antenna cable, or its proximity to other nearby equipment. Antenna cables or antenna distribution systems can fail, so you'll need to check them accordingly.
Take the problem wireless system to a different location outside your venue or building. Try the mic in your new location after scanning for a clean frequency. If the mic works, then the problem is coming from the local environment at your venue or building. If the mic still drops out, you could have a faulty mic or receiver - send them out for service.
Once your mic is working correctly, slowly add in (one-by-one) the antenna distribution, remote antennas, and other wireless systems until you have a complete working system.