No, only Avast Premium is installed on my system.
Besides it I also have Avast AntiTrack Premium and Avast Cleanup Premium.
Certainly strange, I can't recall seeing this in the forums before.
I can't see why it would work if you already have an AvastUI window open, to my thinking that would mean the scan isn't connecting correctly with the UI interface.
Are there any other UI anomalies that you have noticed ?
I will try and draw some attention to this topic.
Just one point, what is the purpose of running a right click scan ?
This is much depreciated with a resident on-access antivirus as new, modified or running an executable would initiate a file shield scan.