strange android system behavior if application is running more than ~8 hours

im currently building a digital signage app, which is running on displays which are based on android 7.*. Everything is working perfectly, except a weird OS behavior:

After a while (6-9h) of running the app, android minimizes my application, i don't get any error logs nor do i get a exception thrown.

My workaround solution is that im reopening the app every 2 hours, this is working fine, but its not what it should be.

I already tried it with WakeLock, Keep alive, Kiosk Mode, nothing seems to be working.

Does anyone have a idea how i could solve this android behavior?

I am getting pretty frustratet. PLS help