Avast mobile security running a scan for 3 days!!

I have installed the free version of Mobility seurity and I ran the scan om my device (Android)
The scan is running for 3 days now and Stop every time the display goes to auto lock.
I can only rise the time up to 30 min. and when the phope goes to lock avast stop an I have to
restart the application from begin. :frowning:

Someone can help me?