What happens here in the training of a Keras model? : I am new to Keras development and I have tried to create a Keras model with my own data. After about a few epochs something strange happened (like a staircase) that I can't explain to myself.

[Result of the training][1]

Do you know by chance what the event after about 270 epochs means?


  [1]: https://i.stack.imgur.com/EdklU.png