I’ve been experimenting with this issue a lot over the last few days.
Try as I do, I can’t get the problem to replicate for the vertical border between boards. That seems to be properly coded for pieces to find the correct hex centers.
When there is a “technically” similar vertical join between zones, the pieces drop into left zone and right zone stacks, which don’t automatically combine.
I’m suspecting the coding for zones is lacking the steps that solve the issue between boards.
Daniel