As a temporary fix, updating the voice settings by disabling the "say ok google" functionality has worked.
Samsung Community forum has a discussion on this. ("No recently used app glitch")
Seems the issue is with "ok google" functionality.
According to a poster on Samsung (I am paraphrasing), which makes logical sense. The ok google mic stays open and opens apps and performs other tasks and in that some how after using the ok google functionality the phone no longer recognizes that the apps that were opened prior to using ok google, are still opened.
My question is does Google or Android fix this?
Seems like although it's caused by ok google functionality and thus a Google problem it is the device recent app key that is not responding correctly or with the correct status displayed, regarding the recently used apps.
I cannot find a Google forum with this issue being discussed.
The Samsung forum seemed, rightfully so, to totally absolve themselves of any responsibility to fix it.
I enjoy the ok google functionality and my Android based Samsung Galaxy s6 was shipped with that functionality included.
Does anyone know who will fix this? And how we draw their attention to it?