My xls file is exporting and starting with wrong letter.
It's starting with B letter instead of A, that is the correct way.
I attatched an image that examplifies.
And instead of D the file is going directly to E column.
All the columns are there, you just can't see them because they are very small. This happens because there is some misalignments in your report design. A single pixel to the left or the the right is enough to make Jasper use another column.
Just make sure there is no space left between two text fields.