Robin_P, some products are experiencing audio issues related to HDMI. You would be able to find additional information on the following link. The information provided was given by an Intel Engineer.https://communities.intel.com/message/218663#218663
We always recommend customers to use straight connection. In your case, the receiver is working as an adapter. That could be the reason of the behavior you are getting when it is between the NUC and the TV.
We tried to make as many third party components compatible as possible, but do to the sheer quantity of these third party components we cannot always guarantee compatibility.
You can also try installing the latest Graphics drivers available Intel® Download Center