This message was posted on behalf of Intel Corporation
Correct, you are right, that is not the ideal situation and the NUC does not supposed to work like that, so, let me apologize for any inconvenience.
Based on the fact that you already replaced the power adapter, that indicates that this problem could be related to the NUC itself, as you mentioned could be any loose mechanism inside the NUC or the power port itself.
The NUC has 3 years of warranty and we can always replace it for you, if you are interested in the replacement, please get in contact directly with us through chat, email, phone or online support, you just need to select NUC on product type and you will get those options:
Any questions, please let me know.