Today I turned on my calculator to solve some problems. As soon as I turned it on I noticed that small black boxes were scattered around the screen and whenever I pressed a key/ number it wouldn’t appear on the screen. I took off the batteries and tried to unscrew the back of the calculator to see if it would work. Once I placed everything back into place the previous solid black boxes became glitchier and once it turned off by itself and back on it then had a solid black box. Is this an internal problem and is there anyway to fix it? Or would it be best to buy a new calculator all together?