input and target output batch
Troubleshoot 101: How to fix your neural network
Print/display a couple of input and target output batches to ensure the results are fine. You can also try to input random data to see if the error continues. If it does, it means the neural network is turning data into garbage. So you have to start debugging layer by layer/op by op to locate the issue. Even if your data is fine, the code that pushes the input to the neural network might be broken. Hence, it's important to check the input of the first layer.