Hi ,
You will fail to reproduce it in fresh project, I ve tried it with also no luck. This tends to happen when project is not simple and have deacent amount of content in it. In at least two different projects of mine (both quite big) this is happening. I would recommend reproducing it in shooter example project or infiltrator demo, both of those are huge projects and I bet you will reproduce it quite easily.
As to what is causing it. When You play from Play In Standalone old game dll’s are loaded instead of fresh ones. Note that when You delete Binaries folder, then recompile solution from VS so that only one game dll will exist, it will start to work as expected.
Also recompiling from within Unreal Engine fixes this issue.