Keyboard problem with Inspiron 1300

I recently starting having keyboard problems with my Inspiron 1300. Now when I type "t" I see "t5" on the screen. And if I type "y" I see "y6". The same thing happens with many other keys. It seems many are stuck together somehow.

I ran the Dell Diagnostics and there were many errors on the keyboard tests, with errors like "Invalid scan code detected".

I've read in this forum that some people have tightened the screws on the bottom to fix keyboard problems but I've done that and it didn't make a difference.

Does anyone have any suggestions?

thanks!