Error in TensorFlow 2.5/2.6

[klyack]

Relativistic average GAN with Keras custom loss : TypeError: Cannot convert a symbolic Keras input/output to a numpy array. This error may indicate that you're trying to pass a symbolic value to a NumPy call, which is not supported. Or, you may be trying to pass Keras symbolic inputs/outputs to a TF API that does not register dispatching, preventing Keras from automatically converting the API call to a lambda layer in the Functional Model.
Got same error locally on Python 3.8/TF 2.6 and in Google Colab
P.S. I had to remove model visualization