Electrical issues. Please Help

Hey everyone, I'm having a very strange electrical issue. I tried to install these cameras that plug into the yellow RCA connectors in the back of my Kenwood DDX9903S (I'm also using a Maestro if that info helps).

Backup Camera for Car, Esky Mini HD Color CMOS 170° Wide View Car Rear-view Camera with Night Vision, Waterproof Parking Camera Side/Front View Reversing Camera for Truck, Car, Travel Trailer SUV

https://www.amazon.com/gp/product/B00H3ZN3JK/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

Backup Camera License Plate Frame, Esky Car Night Vision Rear View Camera with 170 Degree Viewing Angle & 7 Bright LEDs, Universal Waterproof High Sensitive Vehicle Reverse Camera Assist Security

https://www.amazon.com/gp/product/B00GMC8QXI/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1


These cameras have a red power wire coming out of the RCA connector that I tapped into the Accessory 12V line going into the radio. For the front camera, I connected the ground to the junction where the battery's neg. terminal connects to the frame. For the rear camera, I connected the ground to the frame connection above the driver's side rear wheel. Here's a wiring diagram


After setting up the cameras my accessory wire no longer holds 12V. It was holding 12V before I installed the cameras, because I checked the line with multimeter before I tapped it.

I think I checked all the fuses but I'm not positive. I checked all the fuses under the hood, as well as under the steering wheel. It looks like they are all good. I have disconnected both cameras, but I am still having issues.

Here are the symptoms:

1) When I first installed the cameras and tried to test them, the radio wouldn't come on. I measured the accessory wire (red) and it was reading 4V, but the power line (yellow) was reading 12V. After about 10 minutes of trying to debug and checking the fuses, I noticed the accessory wire had fallen to around 80mV.
2) When running the car, the radio turns on, but dies and then comes back on as if its resetting due to a brownout/low voltage. The radio seems to work ok when the car is in park. The resetting issue comes when I'm in drive.
4) I used to be able to turn the car off and the radio would stay on by just turning the key one click (putting the key into the accessory position, not the off position). Now when I do that the radio dies.

Does anyone have any idea how the accessory wiring works? What would cause this wire to lose voltage intermittently like that?