I have boned a laptop and when I moved the bone for the screen, it goes fine, but a vertice on the laptop goes up or down all the time when i move the bone for the screen. How can I fix it though? I looked at it to see if there were any weight paint at that area but no.
In Edit mode, select the vertex, open the N panel, you'll see if the vertex is part of a vertex group it is not supposed to be part of, you can remove if from this group if you press the X button.
Blue doesn't mean the selected bone or group has no influence on these vertices, it might be a very low influence, to check the real zero influence in Weight Paint mode you need to display the Zero Weight option of the Viewport Overlays.