Animation time increasing

Hello,  very occasionally a weird thing happens in my copy of SL 360. Watch the attached video, and notice how the animation time, encircled in red, is increasing on its own very quickly. It will continue up to 59 seconds and then stop, but will start again from zero when selecting another object on the screen. There seems to be no way stop it except closing the application. And when reopened, the problem is gone. I don't know what I did to cause it to happen. I have always installed updates as they are released. Thanks for your consideration.