I just completed putting a V3 into an amatuerradiokits case with Nextion 2.8 front panel and had this same issue. The problem turned to be the 3 pins that support the volume control connection on the aux board were shorting on the metal left post that supports the front stand on the bottom of the case. To resolve this I located a short little plastic cap and placed over the post which eliminated the short. This is not an issue with the 2 line lcd display as the aux board mounts much higher on the front panel.
Alan
NX4J
