Gap measurement for aluminum window sill in the clinker

Hello everyone,

I need your opinion on a window issue.

We had aluminum exterior window sills installed in our brick construction.
However, at some windows we have a large gap in height (see photo, about 2cm).

A question for the sealer: The gap is too large for a silicone joint.
A question for the mortar work: The gap is too large for a mortar joint.

Since we will have a meeting with the builder soon: What would you see as an optimal solution here?

Thanks for some helpful tips
Ben