Canadian Payroll Tax Issue with Bonus and Lump Sum Payouts

If we try to pay a Bonus or any paycode with PayType of "Bonus" OR any paycode with a Reference of "Lump Sum Payout" on a Batch without their regular pay then only 10% tax is deducted.  We paid a Lump Sum type a year ago in a batch by itself and proper taxes were deducted but now it only takes 10%.

Here are the results of my testing:

Taxes for paycode set up with PayType "Bonus"

                           Bonus+Salary     Salary only      Difference      Bonus Only

Emp1 (40K/yr)      576                         248                      328              125

Emp2 (85K/yr)      1340                       849                     493                125

Taxes for paycode set up with PayType "Regular Pay"

                           Bonus+Salary     Salary only      Difference      Bonus Only

Emp1 (40K/yr)      670                         248                      422              193

Emp2 (85K/yr)      1385                       849                     536               189

I get the same results if I use any PayType with Reference of "Lump Sum Payout".  

I have instructed the user to use PayType of "Bonus" if paying on a separate batch in which case the add'l taxes on the Bonus amount would be $328 and $493.  If she wants to pay it as part of a regular payroll batch, to change the PayType to "Regular Pay" or use a separate pay code to deduct $193 and $189.  Still a huge difference!

I believe this to be an issue with Canadian Payroll, possibly in GP2010 or later.

Has anyone else noticed this or found a solution to this?