I have frequesnt problems with MEP elements disapparing while doing ordinary tasks not related to view, graphics, visibility.
For instance, I begin drafting Mech. System number 3, change several views, and after going back to plan view, my Mech. Systems 1 and 2 completely disappear. I can see particular elements of invisible systems when I hover over them with pointer.
Switching "reveal hidden elements" back and forth returns their visibility, but this cannot be good solution, as I did not hide any element myself.
The other problem is though invisible elements are restored, all tags related to them disappear permanently.
I could not do any large serious project with danger of all tags disappearing without any particular command being applied and no option to recover. This looks to me as uncontrolled environment.