Problems with bookmarks and subreports

[picht]

In Jasper reports 6.1.1 one can add a bookmark to a test field using bookmark property and level.

I've dione this in a main report (i.e. main.jrxml) and in some subreports (i.e sub1.jrxml and sub2.jrxml)

In PDF it should look like this:

1 BM1 (main)

2 BM2 (sub1)

3 BM3 (sub2)

4 BM4 (main)

But this is what I get:

BM3, BM2, BM1, BM4

Any idea, what goes wrong and how to fix?

 

Thnx in advance

Carsten