Reproduction steps:
1. Open the user’s attached project
2. In the Hierarchy window, right-click “Cube_Lod0” > “TestSetLod”
3. In the Inspector, observe that Lightmap is added to “Cube_Lod0” GameObject
4. Enter Play Mode

Expected result: Lightmap remains on the “Cube_Lod0” GameObject
Actual result: Lightmap is removed from “Cube_Lod0” GameOject

Reproducible with: 2020.3.38f1, 2021.3.9f1, 2022.1.15f1, 2022.2.0b7, 2023.1.0a10

Reproducible on: Windows 10 Pro 21H2

{code:c#}
[MenuItem("GameObject/TestSetLod")]
static void TestSetLod()
{
int index = 0;
Vector4 v4 = new Vector4(0.7555f, 0.7555f, -0.00306f, -0.00306f);
GameObject go = Selection.activeGameObject;
MeshRenderer mr = go.GetComponent<MeshRenderer>();
mr.lightmapIndex = index;
mr.lightmapScaleOffset = v4;
}
{code}