AppleTV 4K (2017) increase volume by itself

Hello,

Here is my setup:

Sony A1 TV -> HDMI3 ARC -> HDMI Bluesound Amp.

Sony A1 TV -> HDMI2 -> Apple TV 4L 2017

In AppleTV settings, Audio control Auto (IR TV).

Since 6 month, sometimes the volume rise up to 100% continuously when a catch the remote control. If i press the "down" volume button, it raise down the volume but if i release the button, immediately the volume raise again until 100%.

With my iPhone camera, i can see that IR signal is from AppleTV remote (IR Led flashing).

• I unpluged the Amp: same issue, IR signal still flashing.
• I Switch off the TV: same issue, IR signal still flashing.
• I unplugged the AppleTV: IR signal stop flashing. After reboot, all is fine.

I've factory reset AppleTV settings: same issue.

I've replaced the legacy AppleTV remote by the new one: same issue.

I've replace the AppleTV by my second one and re-appair the remote control: same issue.

AppleTV tells remote control to raise the volume, i don't know how.

Any help from an expert would be nice, i don't know what to do.