Timer not accurate

Im brushing more than a few seconds in excess of 2 minutes (brush always on teeth) yet timer often records only in the 1:50s. Makes it much less helpful as a motivating tool. Have checked settings and see nothing that would correct this. Would also appreciate some kind of help or troubleshooting tool so problems could be addressed.
... Weeks later the problem persists.
I will make a paper chart. What good is a motivational tool that doesnt credit your honest efforts?

Danac44 about Oral-B