Problem with queues on my RB750

Hello,
I have RB750 that works as transparent traffic shaper. It’s configured by instructions I found here: http://wiki.mikrotik.com/wiki/TransparentTrafficShaper
Difference is that I have one more mangle (because I want to classify windows shares and some other lan services too as lan traffic).
Also I have more queues because I want to limit traffic to some ip addresses.

When I limit traffic to 4mb/s for download everything work as it should. But when I limit downolad to 9mb/s my limit is dropping. When I disable queue download speed is increasing to speed of my connection to internet (16mb/s).

I found that another member have problem like mine: http://forum.mikrotik.com/t/relation-upload-speed-limit-to-download-speed-in-q-tree-adsl/43549/1

In attachment is complete configuration of my mikrotik.
zamt.rsc (28.5 KB)