please try with a basic example :
sliding text or just display some characters(abcdefg).. in this way you can determine whether the issue is only in a specific area of the LCD?
It might be a loose connection in the Grove LCD module
 - (but usually the display is fixed tightly to the PCB)
After deciding that if improper placement of the LCD is the issue, you can try removing the LCD part & repositioning it. (I haven't tried though. sometimes it might be worse removing it, if you can't place it again to the correct location)