Lukas,
about : I cannot reproduce this problem.
i send you the *-mcz file about my test.
You only need update the initialize method with the Pier name instance in your image.
( it's work with same name 'pier' )
nomeKernelA := 'pier'.
nomeKernelB := 'pier'.
After when you browser the example :
1 : click SiteA
2: click SiteB
2A) click on Information link
2B) click on Introduction link
All is ok at this step.
3: click SiteA and after a sub link of it ( Information link for example in the
default Pier )
4: click SiteB NOW this page are update at point 3 selection
NOT at the last 2B state.
I hope this help you to reproduce the problem.
I remain in every way on disposal for eventual explanations.
Thank,
Dario