ONNX Runtime error: node->GetOutputEdgesCount() == 0 was false. Can't remove node

Question

I have a simple Keras RNN model, composed by embedding, LSTM, and linear layers:

loaded_model.layers

Out[23]: 
[<keras.layers.embeddings.Embedding at 0x2275dc1f6a0>,
 <keras.layers.recurrent_v2.LSTM at 0x2275dc8d5b0>,
 <keras.layers.core.dense.Dense at 0x2275dd17730>,
 <keras.layers.core.activation.Activation at 0x2275de3ee80>]

The model works well in Keras when dumped and loaded. I converted the loaded model to ONNX opset 15 using tf2onnx.convert.from_keras, but I get this error when I init the InferenceSession object:

onnxruntime.capi.onnxruntime_pybind11_state.RuntimeException: [ONNXRuntimeError] : 6 : RUNTIME_EXCEPTION : Exception during initialization: D:\a\_work\1\s\onnxruntime\core\graph\graph.cc:3275 onnxruntime::Graph::RemoveNode node->GetOutputEdgesCount() == 0 was false. Can't remove node sequential/lstm_7/transpose as it still has output edges.

This is the relevant node in Netron:

Indeed it has output edges...

I don't want to see this error. Is this some kind of optimization that I can turn off in InferenceSession with disabled_optimizers=...? (this argument is not documented unfortunately)

Thank you.