BitDefender does a system scan, but only partially

I am using BitDefender and it can do system scans to check for viruses, however, once the scan gets to 8% complete, it suddenly says “Scan complete - no threats detected” and ends - as if it couldn’t be bothered to scan the remaining 92%. Wondering what could cause an antivirus to do this?

If I do have a virus, is it capable of sabotaging antivirus software to prevent it from doing its job; kind of a preemptive strike?