What I did… I created a custom flag column ‘Hi Level’ for which ‘no’ meant I didn’t want to see it. I then created a custom filter to filter on that flag. When I had summary tasks with ‘Hi Level’= yes I was not seeing any chains of driving predecessors. When I unchecked ‘summary tasks’ the chains were restored. So then I set ‘Hi Level’= no for all of my summary tasks and it solved my problem – filtered or not, I could see the driving predecessors.
Today, when I went back to set ‘Hi level’ to ‘yes’ for a few of my summary tasks I found that the driving predecessor chains remained when filtered – regardless of the status of the Summary Tasks checkbox. So maybe I need to find a specific summary task that triggers this, but for now, I can no longer reproduce it.