The longer the cable (and the gauge of wire) will cause voltage to drop due to resistance in wire…
Try using the original stock cord with power supply and an extension cord to the power pack, If your problem goes away then you know it is due to the voltage drop.
The link below is a solution for long wire runs, using outdoor low-voltage landscape lighting wire.
https://forums.wyze.com/t/powering-outside-cameras/199388/3