I'm glad it works. If the data you see is what you expect, I won't investigate on the apparent inconsistencies in the Server log.

About the grouping feature, I suppose that the list shown in the first page is dynamical (i.e. it can grow and shrink in time) and it is produced by a COMMAND mode item.
Is the list of sub-events for each event also dynamical? Then I think you need to introduce a new COMMAND mode item for each event in order to list all the sub-events.
Your second page can explicitly subscribe to the details of all the events needed.
You can take advantage of the DynaMetapushTable support and subscribe to multiple items in the same table; all the rows belonging to different items will be listed.
You can have those rows sorted primarily by event, then by sub-event, by playing on the sort configuration and using an extra hidden field, that you can determine on the client side, as the sort key.