Hi,
Thank you for your reply.
According to your reply, seems that there is no relationship with I mentioned Windows Update Delivery Optimization.
But we haven't heard any similar issue with what you said. Also I tried to search on Internet but not found any related issue about yours.
If it is available for you, we would recommend to test by setup a new Windows 10 IOT. If same issue occur on it, we could re-setup and monitor it with process monitor, then filter the process to check if any related actions were performed after setup.
Bests,