It could be a keyboard issue so the test is well known. Try an USB KEYBOARD. If that works you see how much a new laptop keyboard is.
If not I look for malware or the old ACCESSIBILITY settings. No OS noted so I can't be more detailed. Also does it do it when you reload the OS?
The touch pad stopped working and the key board suddenly started doing this: the shift key adds a zero automatically when stroked, the r key adds a 4 the same way. This happened after a day of trouble free use...no help from Toshiba.