SharePoint rootsite rename

Hi all, I am having a weird issue: 

- I have set my SharePoint root site as a hub site

- I have changed its title

- For me, the new title appears, also I have tested it with a test account with normal user permissions and that works feen (title appears).

- I have even changed the default language eng --> Dutch and good (new) title appears. 

- Strangely some of the users see "SharePoint root" as the site title. 

- I have used the Set-SPOHubSite command but it didn't fix the issue

- Within this tenant, we are working with only guest users, but guest users have a 'members' role in Azure AD. (Perhaps it is related)

Please help!