I think that the ability to expand the folders comes and goes, but I can't figure out what causes that to happen. At the moment, the bug seems to be persisting, and I can't find a workaround.
I tried a brand-new solution with just an ISLE project in it, and it allowed me to open subfolders, so I haven't narrowed it down to why it breaks some solutions and not others.
I am having this same issue and posted a separate thread about it before seeing your question. Here's where I posted my question:https://community.flexerasoftware.com/showthread.php?219488-ISLE-with-VS2015-breaks-navigating-my-solution
