Dynamics 365 FO / AX - thoughts on application development and customizations

In Dynamics AX 2012 if General Ledger module is setup to validate Check sales tax by entering either "Warning" or "Error" in the "Check sales tax groups" field, then Dynamics AX will throw an error (stop execution) or issue a warning in the infolog if it encounters a tax setup error when doing calculation of tax. The error looks like this: As you might know the tax calculation is based on getting the intersecting tax codes connected to the item tax group and the tax group of a given source document line. In this case I encountered we wanted to diagnose the origins of the error, because the error occurred when changing a customer group, which we thought was a bit odd. Digging a bit deeper, the error was not related to changing the customer group, but instead related to the following recalculation of credit limit on the customer that Dynamics AX wanted to perform. I traced the error to the class Tax and the method insertInterSection. Seing