Recent apps - one app missing

[Kayman-SE]

In the recent apps list, my browser goes missing. Sometimes, but rarely, it reappears.
The browser app is Boat Browser. I've tried both restart and reinstall.
Fir what I know it's the only app with this behaviour.
Chrome works ok, it shows up in the list.
I suspect one the many per-app permission Android 6.0 gives us, but haven't been able to fix it by changing them different ways.

 

[orangecroc]

Have you made sure it has been Whitelisted so that your phone doesn't kill it.