Can you check the IFC file exported from Tekla in an IFC Model Viewer like Solibri or Tekla BIMSight?
Is the Beam a Beam in the IFC Viewer too?
If not, Tekla export might have the problem.
If it is, then the ArchiCAD import may be erroneous. In that case it may have to do with the fact that it is an inclined Beam.
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