Are you seeing a decreasing loss scaler after 217 epochs or which operation triggers the division by zero error?
If the loss scaling is going down rapidly, your model output or loss might be an invalid value (NaN or Inf) and thus all steps are skipped until the loss scaler dies.
It’s strange that this issue happens after so many epochs, so I assume your input data is clean.
Could you check the max and min absolute value of the activations during the training?