Here are several reasons which can directly affect your mining speed and results.
1. It has been noted that some antivirus systems reduce the mining speed.
2. If you are running any kind of ad-blocks on your browser, mining results can be affected. Turn off the adblocks before you run mining app
3. Poor RAM and low processor capacity of your computer.
4. Disruptions to Internet connectivity may cause error in saving your mining results.
5.Your WIFI network settings /web safe settings/virus safe can interrupt mining tool.So if there are any security updates done by your broadband provider,you might want to check if that is affecting your mining .
Please keep all these points in your mind while doing the mining.