Hi Ivan,
I built your project and took a look into it. The result is that your model outputs an array of [1][10][4] and you are givving it an output array of [1][6]. So the problem is at your output of the model. I think you have to check again the conversion to tflite (if pure tensorflow code works correctly) and check it with netron.app. I really do not know what the output should be, so if it has to be an array of [1][6] after the correct convertion you will see this at netron.app.
Besides that there are some other coding issues at your project that I managed to overcome…but they are minor and firstly you have to check the conversion.
Happy to help again. Ping me anytime.
Best