In depth learning yolov5 training, the map suddenly drops, so does the adjusted learning rate. What is the problem? Is there a solution?

[ZZM11]

In depth learning yolov5 training, the map suddenly drops, so does the adjusted learning rate. What is the problem? Is there a solution?
The first is map
The second picture is train loss
Page 3 is vai_ loss
Please give me some advice
The two lines are that the learning rate decreases from 0.01 to 0.005