Core model no display

Hey all just wondering if anyone has any experience with the lcd rail on the core model. Had an issue with a broken fpc connector, replaced the connector and the screen was working fine but then developed an issue where once put in sleep mode would not display anything until fully powered off and on again. Changed the fpc a second time and this time had nothing on screen and the fpc got hot instantly guessing wasn’t aligned properly. Sent it off to a repair shop so they could put the fpc on properly but there is still no display even with a new lcd so my guess is something is shorted but everything is testing fine according to the shop. So just looking for some guidance if anyone has had this issue before and what could cause it or what I could specifically change to fix this issue?