Timer notification only starts on second app closing

[quazgar]

Problem

When I start a timer, sometimes the notification does not show up when I switch from the Simple Clock app to some other app. As a consequence, the timer will not continue running.

Workaround

Activating Simple Clock again and then closing it again worked for me.

Versions

Simple Clock: 5.8.1 (via F-Droid) Android 10