roll-up conflict during workbook build

During workbook build, I get the following error:

<E 2017Apr20 00:37:23.012> Root array has rollup conflict between 'dim1' and 'dim2' for 'scls':007000254610

<E 2017Apr20 00:37:23.012>    Expecting: 005807642120(11152)->00550002s10000(1793)

<E 2017Apr20 00:37:23.012>      but got: 005807642120(11152)->00580764s10000(2151) instead.

However, there are no issues encountered during loadHier operation.

I had a look in the prod.dat file that was loaded and it doesn't look like it have multi-parent roll-up.

How is it possible that the workbook build would encountered rollup conflict when the loadHier did not?

Any insights would be great!

Thanks,

Sean