Problems with a Class D amplifier System

Hello guys, I hope you are all doing well.
I'm new to amplifiers and sound systems so I don't know much about them. I'm building a small sound system for my room, this is the setup for just the subwoofer. I have purchased the bluetooth module, pre-amp and power-amp from AliExpress so they aren't of very high quality.
The Pre-amp and Power-amp run on 12 volts while the bluetooth module operates at 5 volts. The Power-amp is rated at 150 watts max. My Subwoofer is dual coil, 1.2 ohm (I guess it becomes 2.4 ohms when I connect the coils in series), and 60 watts RMS, 150 watts max.
I need your help with the connections. Here's how I did it:
The three wires from Bluetooth module (R G L) go into the Pre-amp, the output wires (two wires) from the Pre-Amp go into the input of the Power-amp. The two output wires from the powe-amp go into the subwoofer.
I'm feeding this system with a 12v 10A power adapter.
These are the issues I'm facing:
1. There is a constant noise in the subwoofer. When I disconnect the audio input wires from the pre-amp, the noise goes away. If I take out the pre-amp completely, there's still a buzz in the Power-amp.
2. The sound volume starts to fluctuate after a while. It goes up and down on its own.
3. Sometimes I hear ticking noises in the subwoofer, it's not clipping because I can hear them even when the volume is very low.
I'm attaching a rough diagram of these circuits. Please pardon me if I'm doing something wrong. Your help will be appreciated.
 

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