Similar things are happening to me. I duplicated a column several times now and it continue to disappear. Also, use hidden lines and the layer cut at 1.50 m and it still shows the building components without cutting at the requested elevation. I am getting really frustrated with Vectorworks. Please, HELP.
I am using Vectorworks Architect 2019.
iMac 27, later 2013
32 GB Ram
1 GB Nvidia Geforce
2 TB SSD