I already reported this bug, but I think it was never solved.
If I create a WPML Group in Toolset Access (let's say "French Pages") and give all permissions to a custom role named "French Editor", users with this role are able to publish and edit french pages, but they are not able to preview drafts (instead they get a 404 page). Actually, the only role that is able to preview drafts in a WPML group is the administrator (not even editors with all permissions are able to preview drafts).
Wordpress, WPML and Toolset Access are updated to the latest version (2.8.10 for Toolset Access).
The company policy does not allow me to share a backup of the website, but the issue shoul be quick to reproduce:
1. Install WordPress, WPML and Toolset Access.
2. Set up two languages: English and French.
3. Create a WPML Group for the French Pages.
4. Create a custom role ("french editor") who can only edit French Pages.
5. Log in as a user with this custom role.
6. Create a page draft in French and try to preview it.
Actually not even the native editor role can preview pages while the WPML Group is active. If I disable/remove the WPML Group, the preview functionality works again.
Thank you for sharing these steps and I was able to reproduce this behavior on my test website too.
If a post/page falls within a WPML group, its preview only works for the native "administrator" role. Lower native roles, for example, Editors or even the roles copied from the "administrator" role, see page not found message.
I've shared these findings with the concerned team and will keep you updated through this ticket.