I watched your video, you scan a file in chest 3 times and it's marked as no virus.
But where's the problem exactly, could you please elaborate..!!
From avast tray right-click viruschest scan option not working.But from Avast main GUI it is working fine.It is a BUG.
It hasn't worked for some time (it hasn't just started in this beta), it doesn't work in the regular release version 17.5.2303. Why it would be any different depending on how you access the Virus Chest, is beyond me.
Though I just wonder if it is somehow permissions, but it has worked for many, many, years without issue what they have changed in the Scan interface (its looks like a different screen when the scan is running) would appear to have broken it.