Common Issue: Location
The absolute location of the model origin is different in each or one of the files. This will result in the misplacement of one or more of the IFCs in the merged file. The only solution is to check the export settings to align/export each model with the correct coordinates.
Common Issue: Scaling / Units
Models exported in different units—imperial vs. metric or at different scales—often result in faulty merged IFC models. Specifically, this issue can also arise when working exclusively with metric models. For instance, if the units of the MEP model were exported in millimeters and the units of the architecture model were exported in meters. This last point is likely due to a faulty IFC exporter.
Common Issue: Faulty File
Sometimes the exported IFC File is faulty, the scheme doesn't comply to the ifc scheme, this could be some instances in the IFC file or the whole file - both will corrupt the merging mechanism. If a faulty file is detected it will not be merged, but procotolled. The other non faulty files will be merged togehter and will be availabe after merging is completet. Furthermore the faulty files will be available for you as list next to the merged file after the merged is completed.