I have found that when renaming a variable, if you type in the new name and click on the screen, but hit another variable, it renames that Variable.
Renaming without too much issue
You can also name 2 Variables the same name. Errors out, turns the name section grey and only solution is to delete the variable, make it again and replace it through out the entire project.
Thank you for the report and the two videos. I was easily able to reproduce the issue and I have reported it as JIRA UE-9641 in our tracking software. Our developers will be investigating it further.