Ever since the August 2022 patch "- Made several improvements to achievement processing to improve zone latency." when a raid event is completed, all chat is frozen for somewhere around 30 seconds. We have to wait for all this time to do loot bids, since no chat is being displayed, and then voila! All the achievements spam and we can chat again! Not sure what improvement this change made, but the chat delay is so much worse than whatever the issue was before the fix.
Duplicate of the issue reported in this thread: https://forums.daybreakgames.com/eq/index.php?threads/lag-at-end-of-raid-events.285617/