I have seen this a lot. When I see it, I find the usual culprit is multiple shape nodes. If you go into hypergraph and expand all the nodes you will likely see multiple shape nodes.

I find there are several ways to correct this. Delete history, delete one of the extra node from the hyper graph, this often caused the part to lose its shader node input and the remaining piece disappears. Simply reattaching a shader fixes this.

As I recall exporting and importing also fixes the addition shape nodes. I am not sure what causes it or what the correct way to prevent or fix it is. I recall seeing it mentioned in a tutorial once and the author explained it. I believe the cause and fix had something to do with normals.

That is the best I can recall as it has been a long time since I last saw this problem.