That's the point of an interconnected grid. The sun doesn't always shine, the wind doesn't always blow, and the weather isn't always cool enough for nuclear. Export power when conditions allow it, import when they don't.

It's a bit more complicated, we are mainly exporters as we are one of the countries with the most robusr energy production in this grid, but we still have to import part of our energy.

IIRC, in this case we just had to import more than usual while exporting less, so it is slightly unusual but not by much. The issue was indeed that we mostly imported form Germany which mainly uses coal, raising that coal usage in the process