Problem with image texture name in image node that not match with the texture being used in the model See the vids below that shows the problem.

https://youtu.be/LGhD4H9cn9Y

i was texturing in texture paint mode using the image named "Face X3.png". after heavy tweaking i decided to save the texture into different texture and name "Face X4.png". The problem was whenever i changed the texture in the image texture node the name is still "Face X3.png", even though clearly i was using "Face X4.png" My model also rendered correctly with the texture "Face X4.png".

This problem sometime exist since version 2.7x, i think it was some problem with the image saving feature after using the Blender texture paint mode.
I think you are confusing the name of the file, and the name of the texture slot inside Blender :



The name of the texture slot can be whatever you want (you can change it ie. in the Image Editor).

When you open a picture file, Blender automatically create a new slot and name it as the file. But, if you then change the file, the slot will keep it's old name, which can indeed be confusing.