Hi Sheila @sheila5 ,
It’s not really a bug.
It is meant to help seeing what you do, when certain Modifiers are Added to the Mesh; if you, for instance Add a Subdivision Surface Modifier, or a Solidify, to the Mesh (seems to work with most, if not all* Modifiers), the Wireframe Preview will be visible.
* at least 1 exception is the Multiresolution Modifier (‘obviously’).