[Lesson 7: Resnet-ish CNN ] Why do the loss graphs look like this?

Part 1 (2019)
1

Hello everybody!

After training the last, Resnet-ish CNN I plotted the losses and metrics with:

learn.recorder.plot_losses()
learn.recorder.plot_metrics()

And got the following graphs:

lesson7_metrics
lesson7_metrics5550×3150 204 KB
lesson7_losses
lesson7_losses5550×3150 189 KB

Why did the validation loss spike around epoch number 2000?