We were able to reproduce similar issue in our environment and our developers are investigating it.
Could you please verify that the scan is completed if the anti-rootkit scan is not part of the whole computer scan? To change the whole computer scan configuration, please proceed as follows:
1. Open the AVG user interface and press F8.
2. Expand the Scans item.
3. Click the Whole computer scan and untick the Scan for rootkits on the right side of the window.
4. Click OK to save the configuration.
5. Run the whole computer scan. Is it finalized properly?