This has been happening ever since the latest patch; every day - multiple times a day, we get the same achievements “completed” as a guild.
We did these guild achievements AGES ago (Guild is from 2010), and now they display as if they were completed this year.
It’s both annoying with the spam; and sad that the timing on achievements are now changed.
Will this be fixed soon? Hope so. 
Hey Náia,
I can confirm that our developers are currently investigating this issue, which can happen under some conditions. We unfortunately don’t have more information than that at the moment, and do not have a workaround (other than possibly using some addons), but hopefully this can be fixed asap. 
If you encounter any other bug in game, please do report it to our developers, and they’ll be able to check this out for you. 
Bug fixes are usually published in our Hotfix blogs and patch updates, which can be found in the News section of the main site.
Thank you!
Dear Blizzard,
This has probably been written elsewhere but I’m going to do it again. Please for the love of the Titans fix this guild achievement alert. I get that you guys are busy, I get that this isn’t a great time but everytime (and that is like 10 -30 times in an hour) a guild alert gongs through my speakers, my game freezes for a few secs. It is getting annoying. My pc is fine before you start that standard sentence. And I am not the only one having this problem. Our entire guild has this.
It makes me shiver for launch. I bought the epic edition for the month sub, but also for the early access but what is early access worth if you can’t even play normally.
Hope you guys will fix this because this is really getting annoying. Especially for people who deal with overstimulation from sound/visuals etc.
Please see:-
I too would love to stop seeing this spam.
why are we paying subscription for such bugs to appear?? come on…this started in the cross-faction guild patch
Has there been any update on this situation?
Feel like they’ve been getting worse and more frequent too.
Thank you for your answer.
We think about creating a new guild with zero achievments, so that we don’t have this spam anymore. 
As that can’t be the solution, we all would be very, very happy when you find a solution. Till to that point, please just deactivate the guild achievements completly or somethind like that.
urgh this is driving our guild batty. I’ve bug reported it and discussed it with others and some guild leaders seem to think that’s it’s been a bug for at least a couple of years … but tend to be triggered more when there are a lot of people online.
I don’t know if that’s the case, but I do know it tends to happen when someone comes online in the guild. Not a specific person … and not at a certain point of guild activity … just randomly.
It does seem to be happening more and more frequently. Alongside the one where we get disconnected from blizzard (I think the message is … or similar), and guild chat, roster and various other guild specific things no longer work.
For people who want this temp-gone; Download the addon; “DisableGuildAchievements”.
Until Blizz has found a fix, this works.
my guild is suffering heavily from this
How is this not fixed yet?? Its been driving me crazy, every hour now, same achievements. Its been affecting THOUSANDS of players all over the world, there must be a solution or is this a low priority thing? Just fix it.
Are you still investigating this a month later? Today was the worst spam of all so far.
This is also not a new occurrence. This is something that pops ups again and again each expansion. I’m hoping Blizzard finds a permanent solution this time. 
It was really bad tonight … we had one occasion where there were three lots of guild spam one after the other.
Sadly it’s still the same. Worse thing is that it freezes the game everytime it happens. And a favorite phrase at our Blizz Gods is: disable add ons. Not only have I disabled them, I also deleted them fully but the problem still occurs.
When will there be a fix with the guild achievement bug? we are sick and tired of these major lagspikes that happens every now and then. This has been going on for a looooong time, and people now have to leave the guild while raiding and doing keys as the game freezes, and all these diplomacy achievements etc pops up… We had 3 major spikes within 5 minutes today, first time it happens so often. Please fix this ASAP!
As a quick update, a fix is currently being worked on and tested for this issue. While some bugs may take longer to be fixed than others, rest assured that this one has not been forgotten.
Thank you for your patience.
Looking forward to it, since it started affecting game play. I’m currently running the disable addon because the pop up spam just kept reappearing during combat, and that’s not really convenient.
This should be nr1 prio on bug fixing… wiping us so many times now!
Still no update, and the addon that temporarily fixed the issue seem to bug out a lot now too.
RIP.