Did that taxpayers USED to have more dependents that are no longer dependents (and you removed them from the program)?

If so, it is a weird glitch in the program.  Try this:

1. Right-click the dependent, and delete the "line".
2. If there used to be more than one other dependent, do it again with with the top blank line for dependents (do it again for each dependent that was previously deleted).
3. Re-enter the dependent.

Or override the Recovery Rebate worksheet.