Redmine

I want to update the sub-project of my project. but when i click to save i have an 409 error (conflict).
I check in the log and i have this error :

ActiveRecord::StaleObjectError (Attempted to update a stale object: Issue.):

app/models/issue.rb:227:in `create_or_update'
app/models/issue.rb:1880:in `block in update_versions'
app/models/issue.rb:1874:in `update_versions'
app/models/issue.rb:1467:in `update_versions_from_hierarchy_change'
app/models/project.rb:1033:in `update_versions_from_hierarchy_change'
app/controllers/projects_controller.rb:216:in `update'
lib/redmine/sudo_mode.rb:61:in `sudo_mode'

Thanks