From my point of view, this whole thread has been tracking my single issue, getting the proper locations to show up with the desired zoom level on two different map views. In this thread I have been offered and responded to the different solutions provided by your team that individually created more issues (i.e. the additional Multi-Map issues on top of the category filtering not working). To get this working for my client so I will bring this back to being the issue with Tagalong only on this thread and deal with Multi Map on another thread.
The unresolved issues with only_with_tag (and only_with_category filter too?) response at least that gave me something to work with. I stripped out all the other shortcode filters and I am now getting the correct locations.
Would you like me to add in the removed shortcodes one by one again and see which one kills the tagalong filtering?