1. I use W3 Total Cache plugin. I did not have this bug when I had Object Cache enabled. Now I need to disable object caching. I conclude that author list bug has something to do with object caching.
2. This bug remains both for admin and for non logged in users.
3. I installed plugin version from github.com and now it is better.
4. Now problem remains on the page where I use shortcode with full author list sorted by post numbers. Also on this page I enabled widget which shows the same list but the output number is limited by 10 items.
So now bug is the following: In the widget there are the same number of avatars shown as in the shortcode list. When I change the number of avatars in shortcode the number of avatars dislayed in widget also changes (althought the max number for widget is set to 10).
I also found that when I change Sorting order in widget or in shortcode (so that they differ) everything works fine. No conflict in max number parameter.
Hence I see the bug when there are 2 author lists with the same sorting order. Conflicting parameter is the maximum number of avatars shown.
You can observe this bug on my test website (copy of prodiction) -> https://sandbox.favot.ru/authors/ (Object caching is disabled. Some avatars does not display because it is not production.)
The sortcode I use:
[authoravatars roles=author,contributor,editor,editors,blogger,journalist user_link=authorpage show_name=true show_postcount=true min_post_count=1 order=post_count,desc avatar_size=150]
Widget config is here:
https://dl.dropboxusercontent.com/u/40416848/avatar%20list%20widget.png
Now I fixed this bug by Visibility option of Jetpack plugin. I do not show widget on the page where I use shortcode.
So now it is not so critical. Although if possible, it is better to fix this bug.