The header contributions seem to be appearing and disappearing randomly. Let us have a simple webpage containing a link and a StringContributor. If I click on the link, the page refreshes and contributions appear normally. However, in the subsequent refreshes of that page in the browser (using the browser's refresh button) the contributions are not appearing.
There was already some fix in the HeaderContribution issue in Wicket 1.2.3. Does this problem have something in common with the fixed HeaderContribution issue in the Wicket 1.2.3? This problem does not occur with Wicket 1.2.1.
After a little bit of debugging, I am suspecting that the ,,entries" Set in the AbstractHeaderContributor is not properly cleaned up between the requests.
I have tried to blindly patch the AbstractBehavior according to the latest version in the trunk (there is some additional cleanup in this latest version) and this seems to have solved the problem (however I am not sure, whether this is sufficient).