What will soldering do that is different than 'Pressing fit' The LCD?
Again, I can't stress this enough.
No solder with header = Will not work!
The holes in the PCB are just that, holes. The are there to be used for soldering.
They are not a socket and are not designed to be used used with any sort
of mechanical press fit. The fact that you are seeing anything on the screen is pure luck.
You simply can't use it the way you are trying to use it.
The tutorial you referenced even explicitly warned about not trying to do this.
Time to break out the soldering iron and solder the header to the LCD PCB.
I'm not a particular fan of the Adafruit tutorial either, but I referenced in because
it was referenced in the original post that said:
Ok so i followed this tutoial ...
I was trying to point out that essentially the very fist step of the referenced
tutorial was not being followed.