A 1-AWG wire is over 1/4 inches thick. Normal home wiring (120V) is 14 AWG for 15 amp circuit or 12 AWG for a 20 amp circuit. (The bigger the number, the smaller the wire.)
14 AWG house wiring (120V) runs all over the place with little voltage loss. But that’s big wire at 120V. Voltage matters. The lower the voltage, the more the drop. The higher the amperage, the more the drop. And, of course, the smaller the wire, the more the drop.
The cameras operate at 5VDC (not 120VAC). A typical USB cable might have power conductors of 22 or 24 AWG. When you buy them, it’s sometimes impossible to find out the actual conductor size.
For the sake of argument, lets say you have 22 AWG conductors running 25ft at 5 VDC and .7 amp. That gives you a voltage drop of over 1/2 volt or over 11%. String another 25 ft after that and you double the drop, putting the end voltage under 4 volts. You can see why that would start causing problems.
BTW, the camera and USB cable connection in the middle of the 50 feet is mostly irrelevant since the the two cables ends are essentially directly connected.
I’d suggest you plug some numbers in the calculator and then change one parameter at a time to see what the effect is.
Another example: Your 25’ cable, perhaps 22AWG, 5VDC and 1.0 amp (2 cams at .5 amp each). That give you and end voltage of 4.19. Now start with that, add 6 ft, 24 AWG at 0.5 amp. The end voltage is now 4.04. That’s way below the nominal 5VDC and not at all surprising that it causes issue.
Bottom line, you are best off getting as close as possible with 120V power before switch to 5V with the adapter.