LCD displays properly intermittently, otherwise backlit grey: Why?

Replaced front glass/lcd/touch screen a few days ago. Since then, after the screen autolocks, about 50% of the time after I hit the home button, the screen comes on as it should. The other 50% of the time, it lights up but is solid grey (backlight comes on, so not black, but no image). If I turn off autolock – once the display is on, it stays on as it should (it does not randomly go grey). When grey, the touchscreen still works and a screenshot will not be grey - the screenshot is of the image that the lcd SHOULD be displaying. Could degreaser help? I did not clean the contacts with windex when I put it back together. Could the connection just be loose? Could it be a faulty lcd?