Solid Body Converting to Surface & "Delete Face" Not Working in Fusion 360

[mkbstudies]

Hello everyone,

(Video: Delete Face creates an empty hole, but moving the body shows the face is still there.)

I'm facing a strange issue in Fusion 360 (Direct Modeling Mode) where my solid body is behaving like a surface body(to some extent), even though some solid operations (like Fillet) still work. Here's what happened:

1. Unstitch that solid body gives various surface bodies.

2. But when I stitch it back, it didn't become solid again.

3. Delete Face creates an empty hole, but moving the body shows the face is still there.

4. Boundary Fill, Stitch, and Thicken don’t work—it stays a surface.

5. If I "Create Component from Body," it also converts to a surface body.

6. Validate Body finds errors and separates the body into groups of unstitched surfaces.

7. Tried clearing cache, restarting Fusion 360, and even importing into a new design—same issue.

What I’ve Tried:

✅ Modify > Stitch (Even with a high tolerance)
✅ Modify > Thicken (Fusion doesn’t recognize it)
✅ Boundary Fill workaround (Adding an enclosing box)
✅ Delete Face + Heal (Doesn’t work)
✅ Export as STEP/IGES/SAT, re-import (Always imports as a surface body)

Observations:

Fillet works, which suggests Fusion still sees it as a solid in some way.

Moving or scaling it slightly doesn’t fix the issue.

Other tools like Replace Face also don’t seem to help.

Any suggestions?

Has anyone faced this before? Could this be a deep geometry corruption? Any other tricks I should try before rebuilding the model from scratch?

Thanks in advance for any help!

[HughesTooling]

Edit. After rereading I assume this is an imported body? If not why are you working in direct mode?

Hard to say without seeing the model but have you tried running validate on the model before modifying anything? Validate is only available without history so the new "feature" where all imports will have history enabled is not a helpful! So first disable history, then from the inspect menu run Validate and see if there are any errors.

[TheCADWhisperer]

@mkbstudies 

Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?