Model training with ssd_resnet50_v1_fpn_640x640_coco17_tpu-8 results in a Tensor / numpy array conflict

1. The entire URL of the file you are using

https://github.com/tensorflow/models/blob/master/research/object_detection/model_main_tf2.py

2. Describe the bug

The script aborts with the error message:

NotImplementedError: Cannot convert a symbolic Tensor (cond_2/strided_slice:0) to a numpy array. This error may indicate that you're trying to pass a Tensor to a NumPy call, which is not supported

3. Steps to reproduce

Follow the tutorial at
https://tensorflow-object-detection-api-tutorial.readthedocs.io/en/latest/training.html

Then, at the step "Training the Model" it comes to using the the above-mentioned script and the error occurs.

4. Expected behavior

Iniformative output on the training progress as described in the tutorial.

5. Additional context

See full dump attached.

6. System information

• WIndows 10
• TensorFlow 2.5.0
• Python 3.9.5
• No GPU, no TPU, just main CPU.

dump.txt