I don’t think it necessarily is a problem, but if you disregard the update between step 1 and step 2 and the potentially different optimizer hyperparameters, you are effectively optimizing the shared weights to a sum of the two objective functions. Depending on the size relations of the two, this may make more or less sense.
Best regards
Thomas
P.S.: Is it intentional that you take the second output of actor_critic for both?