I just noticed this in Build 157 but it may be an old issue.
When I Rename a variable with ShiftF6 I get a red box around the variable and it is selected. I then press CtrlV to paste a new name. All occurences of the name are changed to the pasted name. The problem is the cursor is placed at the first occurrence after the initial invocation while the initial invocation remains outlined with the red box. So if I type anything only that next occurrence changes, not all occurrences of the variable name.
It doesn't appear to matter whether any or all text is selected in the red box. Just pasting in the red box moves the cursor to the next occurrence but leaves the red box in place where the Rename was invoked.