https://github.com/rwth-i6/returnn/issues/703

test-703.py

from returnn.config import Config
from returnn.tf.engine import Engine
import sys

sys.path.append("tests")
from test_TFNetworkLayer import make_feed_dict

n_in = 40
model_filename = "test-703.model.001"

def make_net_dict():
  return {
    "output": {
      "class": "conv", "from": "data",
      "filter_size": [3,3], "padding": "same",
      "n_out": 32, "activation": None, "with_bias": True
    }
  }

config = Config({
  "extern_data": {"data": {"shape": (None, n_in, 1)}},
  "task": "train",
  "network": make_net_dict(),
})
engine = Engine(config=config)
engine.init_train_from_config()
engine.save_model(model_filename)

config.typed_dict["extern_data"]["data"]["shape"] = (None, 1, n_in)
config.typed_dict["task"] = "eval"
config.typed_dict["load"] = model_filename
engine = Engine(config=config)
engine.init_network_from_config()

net = engine.network
out = net.get_layer("output").output
engine.tf_session.run(out.placeholder, feed_dict=make_feed_dict(net.extern_data))

So I reported this here: tensorflow/tensorflow#52223