C5c modulation at tx rx

Good morning, I have a c5c in a ptp of 24 km, dish of 30 dbi, it happens that it modulates and drops to tx30 rx30, it goes back to working normally for a while if I change the channel and it goes back to making the same error, c5c new the noise ta down what happens in the mimosa cloud is sp err could someone help me? thankful!