Accuracy of the model drastically drops

This is the output from another run:

Epoch: 47
468 469 Loss: 0.061 | Acc: 97.937% (58762/60000)
78 79 Loss: 0.059 | Acc: 98.710% (9871/10000)
Best Test Score tensor(98.8800)
Epoch: 48

Epoch: 48
468 469 Loss: 1.639 | Acc: 38.638% (23183/60000)
78 79 Loss: 2.302 | Acc: 10.280% (1028/10000)
Best Test Score tensor(98.8800)
Epoch: 49

Epoch: 49
468 469 Loss: 2.302 | Acc: 11.065% (6639/60000)
78 79 Loss: 2.302 | Acc: 10.280% (1028/10000)
Best Test Score tensor(98.8800)