Hello,
I was doing a test about exporting and importing an .IFC 2x3 format model into Revit.
Revit version: Revit 2022
01. Open a sample file: Autodesk Revit Basic Structural Sample Project
02. File > Export > Export IFC, with below setting

03. File > Open > Open IFC File > Select the exported file
04. Result as shown below (this testing has done twice, by 'export to IFC' and 'save file as FC')
The high of the exported model was miscalculated, both model were missing part of the original model.

From the above testing, I have also used a third-party software, and confirmed that the IFC model which 'exported' and 'saved as' were having a correct geometry.
I have tested the hole processes twice, and confirmed that this error can be duplicated.
My question as below:
01: Is there any setting ,that I had missed, before opening an IFC file inside Revit?
02: Since there were two types of error ('export' and 'save as'), what is the difference between 'export' and 'save as'? Which one is preferred under which situation?
Thank you very much for all your time.