nextcloud collaborative "pad" synchronization breaks down with multiple users

Today, in both the metrics and vegas meetings, we had problems using the "nextcloud pad", that collaborative, WYSIWYG, "markdown" text editor. We're trying to use this as a replacement for Storm's Etherpad installation and it worked the last meeting.

But now we were over 12 people in the pad and it didn't work so well. The main problem is synchronization, e.g. one user would "strikethrough" some text but others wouldn't see the style change. This is particularly critical in Vegas meetings as we use that style information to carry information about how the meeting should proceed.

There are also issues scrolling around the content using cursor keys (e.g. pgdown jumps to the end of the document instead of one page down), but that's probably unrelated.