Offsetting projected faces on curved surfaces

Hi everyone, I’m stuck with an issue offsetting projected faces. This is a hobby project, as well as a learning one, so I’m also trying to understand the rules for offsetting faces, especially on curved surfaces like this.

The weird thing is that this specific projection and face offset worked just fine. Then I did a seemingly completely unrelated change to the model (added an extrude somewhere far from this surface) and the offset step broke. I then removed and tried to recreate it, but it keeps failing and I cannot wrap my head around it.

The projection consists of two steps, one projects from the front sketch, and one from the top. Projection itself works as expected.

Then I’m trying to inset these faces and the operation breaks. But again, it worked just fine at some point (I’ve of course tried moving the projection and the offset up in history but with no success). It feels like the model somehow became too complex for this to work, but it is pretty simple.

I know it’s probably very hard to tell based on a few screenshots, but does anyone have any theories here?

Edit: I guess the initial thought my be related to the shell, but it’s not related. It fails in the same way with or without the shell.

Well damn, the second I posted this, after having struggled for hours, I tried again projecting the top ridges into the pill shaped face as well, which I had previously tried multiple times before, and suddenly it worked.

I’ll leave the post up in case of anyone else hitting a similar issue, maaaybe it helps. Before posting this, I found a few similar posts and they were all resolved in sort of non-deterministic ways, like “I just remade the sketch and it worked”.

Not sure if this is some sort of bug or if there are rules to this I don’t really understand. Again, like I mentioned, it previously worked even without “overextending” the ridges into the pill face.

Sometimes it’s the order in which you select the faces. :man_shrugging: Had this issue way back when at times.

You had to select 14 faces? Maybe next time try and use the trim tool and lose some of the extraneous lines?