Populating fixed fee from budget to engagement doesn't work (CP 2010)

Symptoms
I have a fixed fee defined at engagement level with 12 billing milestones and 12 revenue milestones (using the $X deliverable).

The same fixed fee is also in a budget (using the revenue recognition rules). When I make a change to the milestones and select 'populate to engagement', the changes are not populated to the engagement.
 
Reason
The total of the revenue milestone amounts did not match the total of the billing milestones.

Resolution
This is because populating to the engagement changes only the revrec schedule of the fixed fee but not the scheduled items. So we can't do this if the totals don't match, otherwise revrec data would be out of synch with the fixed fee amount.

As an alternative solution
1 - when modifiying the schedule in the BAW, make sure that the total recognized amount matches the fixed fee total amount
or
2 - use 2 fixed fees: One for RevRec and one for invoicing.