Surface duplication on joining surfaces

Hi. An issue has suddenly turned up I’m trying to join surfaces, the surfaced say they are joined but it also then duplicated the surface for some reason. It also then created a large number of surface edges etc, some which then become undeletable. I opened a new page, made 2 surfaces and the same happened. What have I ticked, or missed?

Rhino 7 on a Macbook PRO

Any ideas please?

Can you post a file in the “before joining” condition with instructions on how to reproduce?

OK, 2.9 is prior to joining attempt, 2.01 is after joining. Loads of surfaces happening now.

albatross seat2.0.3dm (3.7 MB)
albatross seat2.01.3dm (1.1 MB)

I don’t see a 2.9, I see a 2.01 and a 2.03… Both files look the same to me though.

SelAll shows 2 text dots, 42 curves, 42 surfaces, 8 polysurfaces added to selection.

SelDup shows Found 36 duplicates. 5 curves, 31 surfaces added to selection.

So there are 31 duplicated surfaces in there… Don’t know if that is before or after.

Sorry, It should read 2.0 not 2.9 :roll_eyes:

OK, Maybe this helps?
albatross seat prejoin.3dm (152.3 KB)
albatross seat afterjoin.3dm (181.0 KB)

In the end, I closed it all down. On reopening, it seems to be behaving for now! :crossed_fingers: