This was initially observed in new trigger edit modal form (maybe not merged yet). See the video related to this.

See video:  
 

Steps to reproduce:

1. Open modal form that has help icon in it, for example, LDAP server settings.
2. Go to Users->Authentication-> LDAP settings -> Add server.
3. Click on Configure JIT provisioning.
4. Make browser window smaller, so that whole form would not fit in the screen and would be scrollable.
5. Click on help icon near Media type mapping.
6. Hint box opens.
7. Scroll the form.

Result:
Hint box stays where it was and does not move together with the modal form.
Expected:
Hint box should be fixed to help icon and move together with modal form.