Reason for Huge Jump in Loss For One Epoch Only?
I cannot say for sure, but it seems that it might be an error in the printout. The validation loss doesn't seem to spike, so it seems that the loss may not actually be what is printed.

I can only advise to run training multiple times and see if this happens again. If yes, try toying with the learning rate. There is a small chance that the learning rate could be too high making the loss diverge for one epoch.

Based on your code, it seems that your optimizer clips gradient with an absolute value larger than 1. In a scenario where most of your gradients are larger, this could lead to your model being optimized in the "wrong direction". This could lead to the loss being so large for some epochs.