Cubase 10.5.5 Playhead Randomly Disappear when playing the project, super annoy. 
Mac Mojave 10.14.6
I have this on CB Pro 10.5.12. You’re right, it really is annoying! Still happening for you?
Make bug reports to Steinberg. I’ve submitted it, others have, but no confirmation it’s been logged to be fixed yet. Happens in 10.0.6 as well.
Really really disruptive bug for me.