avast full scan resets

hi i was doing a full scan today and the scan usually scans 1 drive partitioned as 2 , with one being C: and the other F:
now it was scanning C: and the total scan was at 70% suddenly it resets to 1 %
wth is going on?
edit: scan still going and its been 4 hours and now 37%

Starting scan of F: partition ??

no it was scanning C: reaches 70% then goes to 1% and still scans the c partition

bump

What OS?
Which version of avast?
What other security software do you have now or ever had?
If uninstalled how was it uninstalled?

its all fixed, 2 malware file was slowing the scan one that hides an uninstall.exe in a legit program files and some website exploit
(happened when my cousins used it, i give them wot, traffic light and do not track me and still they dont know how to browse)