Interesting. I had a similar problem with my uBitx v6 and a Nextion screen. Mine is 5¡±, and the upper bands would lock up in transmit with no side tone. It would stop only by cycling the power. I must have fixed it by simply moving around some of the cables because it resolved without doing anything else, and I never found the cause. Along similar lines I solved the Nextion noise whine from suggestions here. It¡¯s audible even when the audio is turned way down. Apparently it¡¯s from the Nextion backlight which is minimized by increasing the brightness to 100% but is still annoying. The noise was completely eliminated by putting a 2.5 mH choke in series with the red Vcc power line to the Nextion. I used a FT-114-43 toroid. 70 turns of #22 gauge wire was recommended but I was able to wind a few more turns than that, and my meter showed 3.5 mH. I also put a small 1000 ¦ÌF 16 V electrolytic across to ground for good measure. I also used RG178 in the audio lines.
John Terrell, N6LN