Loading the ESC document on the demo server: https://demo.collaboracloudsuite.com/tdf/index.php/apps/files/?dir=/ESC+minutes I see the attached screenshot - with and without the debug mode on:
Created attachment 129661 [details] broken bits.
Created attachment 129662 [details] with debug mode enabled turning on debug unfortunately refreshes everything - but then paging down a bit I see the attached ...
Pranav debugged this, and I committed a fix; Pranav is working on a unit test ... hopefully will be ready in time for the call =)
Pranav Kant committed a patch related to this issue. It has been pushed to "master": http://cgit.freedesktop.org/libreoffice/online/commit/?id=0e043853ea68e68354de5d9c87a32029319dfdc6 tdf#104695: Unit test for missing tiles due to low socket buffer size