Not being fluent in C++, I followed a few examples I found and they used auto type. So did I.

auto model = tflite::FlatBufferModel::BuildFromFile(model_path.c_str());

This line is problematic. I assumed auto induced the type from the private variable declaration, but I guess it overrides it and is still accessible from other function calls.

Removing auto and just calling

model = tflite::FlatBufferModel::BuildFromFile(model_path.c_str()); works as expected.