I am playing Minecraft Pocket Edition v18.104.22.168 on an iPad Mini 4. For some reason, I am unable to have people join my worlds unless they connect via LAN, but I can join other peoples' worlds just fine. It's the Invite through Xbox Live that's bugging out. The only error message they get is "Unable to Connect to World." LAN Players can join without a single problem, but no one can join my world who is not on LAN. I have tried everything. I can join other peoples' worlds, Multiplayer Servers, and Realms just fine. It started happening right after I updated my game, but then a month or two later that bug seems to have blown itself up and people could join again, but still have to wait it out due to multiplayer causing crashes/rollbacks that go back even before I saved my world by quitting the game in singleplayer mode!
UPDATE: It is still happening. I made sure everyone was on the same version, and still nothing. The rollback has been fixed, though, so that's good, but I am still experiencing problems connecting other people to my world, especially right after updating. I usually have to wait a few weeks after updating before people are able to join my world, yet I can join other peoples' worlds just fine.
UPDATE: It has gotten worse. Whenever I get onto my world, or any world for that matter, the world is not appearing on their Multiplayer LAN games list. I was able to get a multiplayer world hosted by me working by signing another device into my Microsoft Account without signing out on my device, so that it was pretty much two players with the exact same account on one world, except that it was considered a LAN connection and that it meant that two of the same username were on the world, bugging out the commands. Other than that, there is no way to get a working multiplayer world. When I get a chance, I am going to see if it has fixed itself by now. I'm also noticing that it is getting slightly worse with each time it gets triggered, which is usually when I update. Reinstalling the game also doesn't help.
UPDATE: I have tested it and it has finally sorted itself out, and other people can finally join my world. However, in the attachments, there is a screenshot of what just a few hours of one person not on the LAN being on my world caused (apart from extreme lag that is almost to the point of crashing for the entire time). Apparently, it caused my CPU to be 100%. Also, no other apps were open.
EDIT: Right after updating this report and posting the attachment, my iPad bugged out and I had to force restart it, no doubt caused by having people on my world. It just recently fixed itself, probably yesterday or today, so the game is still unstable. What happened is that my iPad froze after going to the home screen, and no apps would open, the App Switcher (double pressing the home button) would not open, and it is completely soft locked. And, when this happens and I shut it off (not power off) and turn it back on, there is a blank and blurred background and nothing else until I force/hard restart the iPad. When it finally sorts itself out, the game's multiplayer features are left very unstable, but usable. A few of the things that happen when I use it right after it fixes itself include crashing suddenly and rolling back the world at least a few days, doing what I just explained with it bugging out the iPad, clearing my entire RAM, causing my iPad to suddenly shut down, draining my battery at light speed, causing ultra extreme lag spikes, freezing my iPad, and a lot of other things.