Transposing from G-Flat-Major to E-Major


I seem stuck: How can I transpose from G-Flat Major (6b) to E-Major (4#)?
If I open the calculator window, the option is greyed out…
Looks like a bug or a limitation to me:

I think I know the reason for this: there is a later part in this song with 3# (F-Sharp-Minor) - so the system can not calculate something that would end up with 13# obviously.

I transposed the parts separately, which worked:
First part from G-Flat-Major (6b) to E-Major (4#)
Second part from F-Sharp-Minor to E-Minor (1#)