iPad Air 1 issues charging after replacing charging port

Hi,

After replacing the charging port on my iPad Air 1st gen, this is the first time I run into this kind issue. When plugging in the iPad, it boots up, and shows the charging symbole and actually charges... BUT... if I disconnect the USB cable and reconnect it back, then it doesn't charge. The only way I can get it to charge is if I shutdown the iPad, leave the cable plugged in, it will reboot on its own, and show the charging symbol again and will be charging.

So, my questions is, why does it stop charging if I disconnect it? Why does it only work when booting up with cable connected?

I've even removed the motherboard and made sure my solder joints were all good. Same results...

Is this a bad soldering job? bad charging port? or something on the motherboard?

Thank you