iPad 6th gen LCD problem

[Arko2]

So.. I've purchased a "partial repair" iPad 6 for dirt from Offerup. It appears as though the digitizer was shattered and removed, and the LCD still connected to the motherboard (but unscrewed). When turned on, the display shows nothing but light grey bars across the screen. The LCD is not cracked. I discovered that people tend to have an issue where a dropped iPad can lead to this same symptom, but slapping it firmly on the back fixes that. I held the LCD in place and tried it, lo and behold the lock screen shows up, but pretty garbled and only for about a second, then it fades away again. Tried also pushing the LCD connector down on the motherboard with a bit of force, which did nothing to change the display. Is the LCD at fault, or the board? Worried I'm going to buy an expensive panel replacement only to realize the current one is fine.