Adding or changing initial direct cost via amendment

My users have been testing adding or changing initial direct cost via amendment and are finding that the system is not recalculating straightline associated with IDC on the lease admin side.  The business case scenario is that someone may have entered the lease incorrectly, so they would need to enter IDC with a back dated transaction date, forcing the system to recalculate as if the correct information had been used in the first place. 

Has anyone else run into this problem?

Is the expectation that straightline rent associated with the IDC should recalculate reasonable?

Thanks!