Brand new Alpine R2-W12D2 makes flapping sounds

[Ejner]

I have just bought a brand new Alpine R2-W12D2 subwoofer and installed it in my cabinet.
The sub is rated for 750 watt RMS and 2250 MAX.
The amp is a Crunch Groundpounder GPX 2200.1 giving 800 watt RMS and 1600 watt MAX
The flapping sound, in the video below, comes when I turn the volume up quite high and then continues after I turn it down to almost nothing for about 5 - 10 min.
I've checked that the + and - cables aren't switched around, and I've tried tightening it to the case to the point where I can not tighten it anymore. I have also tried brand-new phono plugs. Yet the problem continues.
The amp was bought brand new and used for about 2 months after blowing a sub. The sub was way overpowered. The new Alpine sub is also bought brand new.
Any help solving this problem is greatly appreciated

 

Imgur link to video: https://imgur.com/a/KyeSg0s 

[Joe X]

Should be fairly easy to determine what's at fault just swap parts, you have another amp, test with that, use another sub and test, check your gains, do it fast so that you can send the product back for warranty if necessary.