[Plugin: Co-Authors Plus] Capability to edit co-author post

Hello,
I use Co-author plus plugin to enable adding co-authors to pages/posts.
I’ve setted the role of contibutor and capability for editing his own pages/posts but not other’s authors pages/posts.
I’ve got this issue : if a contributor is a co-author of a page/post, he can not edit that page/post.
If I remove the other co-author, then he can edit the page/post.

Is there a way to allow the author who have the capability to edit pages/posts to let him indeed editing posts/pages with more than one author.

Any help would be much appreciated!

http://ww.wp.xz.cn/extend/plugins/co-authors-plus/