Sorry you’re having problems with this extension. Note that it’s not an extension supported by the XWiki Dev team. See “developed by” on https://extensions.xwiki.org/xwiki/bin/view/Extension/Task%20Manager%20Application . Those 2 developers are no longer active so I guess this extension has not been tested / worked on for a while.
Well, XWiki is open source and free and so is the Task Manager extension you mentioned ( https://extensions.xwiki.org/xwiki/bin/view/Extension/Task%20Manager%20Application ).
So no, it’s definitely not the same price
I don’t use this extension but no it doesn’t seem right, since the goal of Kanban is to move stuff around
Maybe there’s some incompatibility issue with the version of XWiki you’re using and the version of the Task Manager you use. Someone would need to test this.
Latest tests I see are on https://extensions.xwiki.org/xwiki/bin/view/Extension/Task%20Manager%20Application#HTestedon
You could check existing issue raised fro this extension at https://jira.xwiki.org/projects/TASKMAN/issues/TASKMAN-83?filter=allopenissues
Feel free to open new issues too. Maybe someone will have a go at fixing them.
If you really need this extension, one option you have is to contact one of the companies offering professional support for XWiki, see https://www.xwiki.org/xwiki/bin/view/Main/Support#HProfessionalSupport
Thanks