LightStanza tries to optimize the data sent from Revit to improve export times and LightStanza viewer/simulation performance. There are limitations however, and in some cases these optimizations can cause elements to appear incorrectly positioned in LightStanza. This typically happens with elements like furniture and can simply be excluded from your Revit export using the "Family Filter," or turned off by layer in LightStanza.
If this happens with elements required for your simulations, you can also turn off this data optimization. At the bottom of the export dialog in Revit, there is an "Advanced" section. Click to expand it, and then toggle off the "Optimize Export Data" option (see attached image).
Please note that for large models this may significantly increase export, loading, and simulation times.