Fails to boot after screen replacement.

I have a customers iPad that came in after he'd attempted a digitizer replacement and had damaged the LCD. It would power on, but the LCD displayed lines(vertical). Upon disassembling, I found the LCD had a small crack near the edge on the bottom. I plugged in my test screen and everything worked fine. The iPad would boot up all the way and function normally. Since I did not have a new LCD on hand, the iPad went on the shelf for a few days until the new one came in. It was disassembled and the battery was disconnected/isolated. When the new LCD came in, it also had some vertical lines but I couldn't find any physical damage to it. Ordered another new LCD. Now both my test LCD AND the new LCD show image fine, however, the apple logo will appear for a second or 2 and then the screen goes black. It does not loop, it only shuts off. I've verified there is no connector damage, I've put in a new battery, verified there is no damage to the battery connector, tried different digitizers/LCD's, etc. My USB power meter shows about 0.7A when its plugged in to charge which drops to 0.45mA after a few minutes indicating its no longer charging. This could be because the battery is already fully charged, but without anything displaying on the LCD, I'm just guessing. I have not yet attempted a restore through DFU as the customer prefers it not be wiped if at all possible. Any advice is appreciated, Thanks!