Layouts p.1. How to make 1 Detail band not overlap another?

[makushatnik]

Hi!

I have 2 Detail bands. Middle part of my Detail band 1 can be stretched by fields - bank name, purpose of payment, receiver, sender, code.. (all of them can be of 5 lines size or even more). All fields have position type - Float.
Layer Detail band - Free Layout (cause of middle part fields stretching), Split type - Prevent.
Detail band's 2 Frame position type - Fixed relative to top.
Datasource - JSON - correctly setted to template.

Here the scheme of my template:

Then I print that template with a long data in text fields, Detail band's 1 bottommost table (signatures) and stamp hides under Detail band 2. Then I print that template with signatures table when it has more then 1 record - it also hides. I can see that when I changes position type for signatures table or stamp to - Fix relative to top.

What can I do to change this behavior?
I need stretching for needed for its fields Detail band 1 with stretched table at bottom and a stamp, after that all data from Detail band 2 on that or a new page (if it's not fit to the rest of the list part). I need a whole Detail band's 2 Frame to be printed on 1st or 2nd page (without breaking its table). 

Screen applied. On that screen 3 records passed to table of signatures. And then Detail band 2 moves to page 2 (as I need if rest place is not fit a whole frame) and table of signatures is disappears.

[makushatnik]

Need I create a bug on Jaspersoft Library? Or I must tell everyone that Jasperreports does not work properly?

Why make a software that does not work? Where do the layers overlap each other?