Going to another app kicks friends out of worlds

When I go to another app, my friends will be kicked out of the world and they'll be shown the message "you have been disconnected" and when I check back, Minecraft will still be open and I can do things like normal but when my friends try to rejoin, they are shown a screen that says "unable to connect to world'" and sometimes, it says "Wow, this server is popular, wait until space opens up" and it's fixed when I rejoin my world, i don't know any more long term fix for it as it'll repeat after I go back in