Quickbooks Under Withholding Maryland Taxes

We use Quickbooks Enterprise Contractor, and Enhanced Payroll. 

We make sure all updates to the tax tables and QuickBooks are done. 

Last year, we had a bunch of employees who wanted to change their Maryland State Allowances to 0 because they owed when they filed their tax return, except they were already claiming 0 allowances. When entering a new employee, I put in their state worked (MD for all), and State subject to withholding is MD (except one PA), with their filing status and allowances from the MW507. I also enter in their local tax rate percentage under County % Rate.

Using three random employees with the same filing status (Single 0 Allowances) in different counties (Harford and Baltimore City), I figured that they are being under-withheld by about $4 per pay (Weekly). 
I am trying to figure out why this is happening. Quickbooks is clearly trying to deduct the state and local taxes from their pay (which is what it's supposed to do and what I want) but I am trying to understand how it is $4 under even when all the information is correct. 
Any suggestions on what to look for setting wise would be appreciated. I am at the point that I believe it's a Quickbooks issue and the only solution is for employees to add extra withholding to their MW507.