I think that is the way it is supposed to behave. When you
Isolate a layer, you are saying to hide all layers except the one I am isolating. It's like on an audio mixing console - there is a SOLO button. When you press that, it turns off all other channels so only the solo-ed channel is playing / recording.
Are you saying that when you then "un-isolate" the layer, the other layers don't return back to their initial shown / hidden states? (Sorry - we don't use layers much here yet.) You might submit this as a feature request to Bluebeam.
Also, have you looked into
Layer Configurations? That might be able to help you some if you save the layer setup as a
Configuration before isolating. You might be able to restore things then by switching to your saved
Configuration. There is info on Configurations here:
http://support.bluebeam.com/online-help/revu2017/Content/RevuHelp/03--View/01--Tabs/Layers/Using-Layer-Visibility--M.htm