Bug? Abnormal battery drain after using timer

I want to report that everytime I use the timer (i.e for cooking pasta Smile) the battery got drained much faster then normal, until I do a turn off-on of the watch, then it return to normal consumption.

I use one-time timer (no automatic repeating) and when it ends I go back to main watch screen using right bottom button: after that, the battery drains much faster than normal, until I do a reset (turn off-on) of the watch.
I think to do the right action to exit from the timer app, so I think this could be a bug in the software, that keeps the timer in a sort of "active" status, draining battery.
Anyone else has experienced the same problem?