This, by it's very nature, is a nearly impossible problem to solve remotely. It'll never be reproducible by anyone who could help and it could be the result of a million different things that have nothing to do with R or R Studio.
That said...
You said you deleted the Local App Data, so I'm inferring you're on a Windows PC rather than OSX or Linux. Correct me if I'm wrong, and in the future it's almost always hhelpful to be up front about that.
When you open R Studio is there anything loaded? A project or documents? And plots in the viewer pane? Or is it a bone standard, stock load?
What happend when you minimize or maximize the R Studio window?
Does anything happen when you use the cursor to move the window around rather than re-sizing it?
How much RAM do you have on your machine?
If you look at the Performance tab in the Task Manager are you low on resources?
Do you have any pending Windows Updates you've been putting off?
Have you tried re-booting your PC?