I watch my 4th gen Tablo through a Roku Ultra direct connected through a Ethernet switch. If I switch to a different input on my TV for a while, when I switch back to the Roku, it either circles on the Tablo app or errors when I select a local channel saying that it cannot retrieve program information. I have to switch back and forth to several channels or restart the app for it to work again. I have verified that the Tablo, Roku, and app are all current and updated. I bought the Roku because of the problems watching the Tablo using the native Samsung Tablo app but it does not seem to be a whole lot better.
Are you leaving the Tablo app open when switching to another input?