Hi Dirk, that attachment worked, thanks.

Even though that capsule shape is joined into one object, somehow not all of its edges got fused together.



Those 3 edges that I show in green above did get connected together - that happened to connect enough parts together so that it will select all together as one object.

However, the edges I traced in red above somehow did not get connected together.

To fix the problem, select that capsule shape, then use Edit/Separate to break it apart, then follow that immediately by Edit/Join to re-join the pieces together. That will then get all the edges joined and then the cracks should be gone from the mesh.

It seems like there must have been a bug in some earlier operation on the capsule part where it didn't glue some of those edges together. Do you happen to have an earlier version of that particular piece, or do you remember what operation you used to make it, there may be a bug in that which should be fixed up.

- Michael