New Display, boots fine, after few minutes presents glitch & goes dark
Replaced the display bezel and LCD per ifixit.
Machine boots, but after machine starts, new display looks great for a few minutes, then the display presents a diagonal, staggered pixel-blocking pattern and goes black.
Hoping it maybe the display inverter cable, is there a process of elimination to test?
From what you describe, you have a.) a loose connection or pinched cable than needs to be fixed or b.) a defective graphics card. I would do what Dave said and try plugging it into an external monitor and see if you get graphical anomalies on both screens. If you do, then it is a defective graphics card and the whole logic board will need to be replaced. This also might be the case because it only shows errors after a few minutes of running once the card warms up, which is in a lot of cases the symptoms of graphics failure. What was the reason for the original LCD replacement that you preformed. If it was for the same issue then it is also most likely a logic board issue. If you try and you are still only getting these issues on the internal MacBook Pro monitor then it is most likely an mistake in the installation process. I have made them before, we are all human. Just go back after testing for graphics card failure and try to look through you steps and see if you missed anything. It may just be time for a new laptop.
Hope this Helps