Steps to reproduce

1. Create few siteaccesses, in my case:

   siteaccess:
           list: [site, eng, fr, it, very_long_siteaccess_name, second_very_long_siteaccess_name, another_one_very_long_siteaccess_name]
   

2. Go to Page tab
3. Try to use More button on the siteaccess list

From time to time, depends on browser window width, you won't be able to use More button. It is impossible to click on it.

You can see the problem thanks to the customer's recording: https://screencast-o-matic.com/watch/cFVFImoF2b