It may be a self-excitation issue. The problem can be alleviated by moving the transmitter and receiver to a distance of more than two meters apart.

If the distance between the transmitter and the receiver cannot be increased, you can leave only any one antenna except the middle one.

It may be that the current frequency point is subject to excessive wireless interference. After turning off the transmitter, perform frequency sweeping at the receiver end. Select a green frequency point for use.

The antenna may be damaged. Try replacing the antenna to resolve the issue.