Not sure what’s happening but I haven’t been able to complete an entire game of any gamemode for 3 days now. 
At first I though it was just Warzone Assault but it’s the same for Firefight and Arena. Randomly it will just send me to a menu screen (that has no icons) from in the middle of the game. I then can’t press anything so I have to restart Halo 5. It usually happens a couple minutes in but in firefight it did it right after we won, during the end cutscene (I got no req points :/). Just wondering if anyone else is experiencing this and what they’d recommend to fix it. The only thing I can think of is to reinstall halo 5 which I’m not too excited to do as that will take a really long time due to the size!
Is your internet actually a piece of string?
Have you tried hard reseting your Xbox? Restart Halo may temporarily fix the issue, but usually hard reset fix everything. I would be surprise if something went wrong with your installation files, and do you really want to install 90+ Gb of data again? I would try the hard reset method first.
What you are describing is like what I’m dealing with. Like you, I am unable to complete matches due to being disconnected mid-game. Whenever this happens, I get the “server disconnected” error message. Does this happen to you as well? Another thing that I have have noticed about this issue is that this has never happened to me before now, which leaves me to believe that this is a server issue, not an Internet connection issue.
Hard reset and use a wired connection for your Xbox if you can.
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> What you are describing is like what I’m dealing with. Like you, I am unable to complete matches due to being disconnected mid-game. Whenever this happens, I get the “server disconnected” error message. Does this happen to you as well? Another thing that I have have noticed about this issue is that this has never happened to me before now, which leaves me to believe that this is a server issue, not an Internet connection issue.
Mine has never given me an error message, just a blank menu screen with no icons. Although I’ve never suffered with this before and it’s only started the past week maybe and my router and xbox ore exactly how they have been for the past year!!