Number of posts is not incremented

[Scalap]

Hello all,

I use the last 5.1.1 version. Some of members off my forum have their number of posts which is not incremented even if they post new anwser or topics.
if i make an "Update Posts Count" from the admincp, their statistics begin ok

I'm administrator and i don't have this issue

This users have a custom usergroup for their primary group ... based on moderator group

Thank's for your help