Please test this on theme Boost for Moodle 3.7 and Themes Boost & Clean for Moodle 3.6 Login as admin Create a new user s1 Go to "Site administration / Messaging / Messaging settings" and enable "Allow site-wide messaging" Open the message drawer and search for user s1 In the search results you should see user s1 Click on user s1 in the search results Click the 3-dot menu right of the heading showing user s1 Click add to contacts On the confirmation dialogue click Add Verify you see the "Contact request send" message Click the 3-dot menu again Verify the menu is fully visible when opened Send the user about 10 multiline messages Verify  you see a scrollbar appear when you have filled the message UI with messages Verify  the contact request messages is always fixed just below the message header showing user s1.