Can you log the device placement, if you can isolate this function with a dummy input:

  
      

      TensorFlow
  

  
    

tf.debugging.set_log_device_placement  |  TensorFlow Core v2.7.0

  Turns logging for device placement decisions on or off.


  

  
    
    
  

  


You can control some multi-thread parallelism with:
Module: tf.config.threading  |  TensorFlow Core v2.7.0