iPad only charges when screen is ON.

I recently replaced the digitizer on an iPad 6th Gen. The iPad turned on and seemed to be charging. The user was not willing to give me the passcode so I completed the repair, clamped it, and left it plugged in overnight. In the morning I noticed it was still only at 3%. I have a meter and noticed that there was charge current only when the screen was on. When the iPad went to sleep the current dropped to zero. If I woke the iPad up with either the home button or power button it would start to charge again. I tried a force restart but no change. I gave the iPad back to the owner and told them about the issue and gave them some things to try such as checking for updates, reset all settings, etc. They say they tried these but it didn't fix the problem. They now say they will give me the passcode so I can troubleshoot this further. Has anyone experienced this? Is it likely a software issue that might be cured by an erase and restore? Or is there a hardware issue that could be at play? I do have a Tristar tester and it reported PASS when I tested it. Any advice appreciated.