Fluctuating Volume only When using radio app

[Amphicar]

Hello,

I just installed my 3rd Joying HU, this one being the 6.2"
JY-UQS04N4G-B

I am experiencing a problem where the radio volume on FM continuously modulates up and down when vehicle is in motion. This only occurs when using the radio app, not with other sources. I would describe it as if you had volume set at 8 and someone was slowly but steadily turning the volume up and down between 6 and 8.

Any thoughts?

Thanks.

[Amphicar]

Figured out the problem.

I first checked antenna connection but problem still existed. I then turned off the feature to reduce volume when backing up. That fixed the volume fluctuating and also restored AM signal lock.