Everytime I think I fixed the issue, more items go missing!

I think both showers without cabin are from store content. Check whether that's still installed.
I'm relatively sure that one of the shower/tub combos comes with the basegame (with the rounded edges). I usually go via bathroom -> showers to get it.
Other than that, the menus under which you find certain items can be a bit erratic. Not even sets (like matching sofas and armchairs) are necessarily in the same menu, even if you expect them to be.