It doesn't appear to be as widespread as the matchmaking issues that plagued Halo: The Master Chief Collection (opens in new tab), but a serious problem has reared its head in Halo 5: Guardians (opens in new tab). Some players are reporting (opens in new tab) their multiplayer progress - their unlocks, commendations, rank, etc. - has been totally wiped, resetting their Spartan to level 1. In addition, these players found themselves unable to connect to multiplayer servers, or booted from matches shortly after they began.
Developer 343 Industries says (opens in new tab) it is aware of the issue and is working on a fix. It's unclear if this instance is related to similar problems that occurred on launch day - though those seemed to clear up within a few hours or after a few hard console resets for most users, and these new problems do not seem so easily taken care of.
I just checked and everything seemed okay on my Spartan, but I'll be keeping an eye out just in case. I suggest others do the same.
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