What is causing this mac to freeze up after booting?

2014 A1502 here, Clean Installed Big Sur 11.7.10 without issue.

Fresh Thermal Paste & General Internal Inspection (No Sign of Liquid Damage)

All connections reseated / cleaned / checked and appear OK.

Tested with 2 SSD's / SMC / PRAM Reset.

Track pad & Keyboard seems to be working fine during SSD Erase / Format & Clean Install, but at the initial choose country set-up or login window everything just freezes up... no movement on the cursor (Which occasionally isn't visible). Power button can turn on and shut down without any issue and the keyboard is typing all the keys in terminal so the KB appears to be fine. Fan spin is normal and it is not getting hot.. The battery status is unknown (Not swollen) and chargers OK, but the issue happens with or without the battery connected. I have ordered a new track pad cable although the previous owner told me they had already replaced that to no avail. No luck booting into safe mode and apple diagnostics reports no issues found ADP000. After all of these steps I have found that disconnecting the internal display & using an external monitor everything is operating perfectly, so my guess is something with the display is causing this freeze (LCD Cable ordered)..... The camera is working fine on the external. I also noticed that sometimes the LCD will not turn on (Can be the LCD Cable) in getting no power supply to it (Again the cable related). I firmly think the LCD itself is OK. Anyone encountered similar behavior before? Ask Ai ? lol

Update: I swapped a complete display assembly from a 2013 model & the issue remains.... freezing at login window. :( So the issue points to something on the board I guess..... Thunderbolt connection issue? Next step to just use Windows on it to see if that changed anything?