Hi MostHost_LA and thank you for your assistance.
While I was plodding through your troubleshooting list, I swapped out my custom fields for the in-game fields and these worked in my test file.
So in a way I fixed the issue. It was your suggestions that pushed me there as my results from troubleshooting were so odd. I basically gave in and shot my code/BP in the head and used Unreal’s.
In reality it evolved into a more troubling problem (see the link if anyone is interested) but in terms of this simplified question the problem is solved.
You were right however, that it is the GeometryCollections that are the prime suspect as I think these are what have been causing me the most problems (again, see link).
Regards,
THC