Part of beams missing

[Anonymous]

Hi people!
I'm having a problem with my beams. Part of them are invisible, and I can't seem to find a way to make them visible again. As you see in the image they have a few lines showing, but most of it is invisible. The ones on the end are behaving most odd, but the other beams tend to show only part of them, depending on what angle I'm looking at them from. Does anyone have ideas about what the problem might be?
Thank you!
(Archicad 19 on a mac)

[Stephen Dolbee]

Is it possible you have 2 beams occupying the same space? Try deleting one and see.

[Laszlo Nagy]

It is also possible that another element with a Building Material with a higher Intersection Priority (such as a Wall or Slab) intersects with the Beam and removes that Beam (cuts it because of the higher Intersection Priority).