Object Snap not using foremost objects but gets lost in complex background objects

I happened to create a post on this in another thread by RichardZ: String Autocomplete - #7 by maxz

Try switching off Isocurves visibility: Preferences > Display modes > Shaded (or Ghosted), I use it that way and I see the behaviour you want. But it depends what you are doing, selecting the object beforehand or after starting the command. In the latter case, i.e. drawing a line, it will still snap to points that are hidden from view by another object.

Max.