That's a Revit limitation, not ARCHICAD. It may happen when you have smaller items, which are meshed (triangulated) upon export and end up as small triangles. Anything below a certain size is discarded by Revit.
Typical situations are inside the turns of a stair or within library objects with smaller details.
--- stefan boeykens --- architect-engineer-musician --- Archicad26/Revit2022/Rhino/Unity/Solibri/Zoom MBP2019:i9Octo2.4GHz32GBVega20/Monterey+Win11 ARCHICAD-user since 1998