我遇到了类似的问题，所以在此分享我的发现，希望能帮助到遇到此问题的人。
在我的情况下，账户合并操作卡在了“合并进度”对话框中，该对话框在“更改帖子所有者…”和“更新用户名…”消息之间来回循环，永远无法完成。
通过查看管理员操作日志 (/admin/logs/staff_action_logs)，我可以看到，尽管在我触发合并后，许多帖子的所有权立即被转移，但没有进一步的操作记录，这证明该操作确实卡住了，而不是仅仅需要很长时间来处理所有帖子。
当我检查错误日志 (/logs/) 时，我发现周期性地出现“Job exception: topic”错误，回溯信息如下：
/var/www/discourse/app/services/post_owner_changer.rb:12:in `block in initialize'
/var/www/discourse/app/services/post_owner_changer.rb:11:in `each'
/var/www/discourse/app/services/post_owner_changer.rb:11:in `initialize'
/var/www/discourse/app/services/user_merger.rb:84:in `new'
/var/www/discourse/app/services/user_merger.rb:84:in `change_post_owner'
/var/www/discourse/app/services/user_merger.rb:72:in `block in move_posts'
/var/www/discourse/app/services/user_merger.rb:70:in `each'
/var/www/discourse/app/services/user_merger.rb:70:in `move_posts'
/var/www/discourse/app/services/user_merger.rb:14:in `merge!'
/var/www/discourse/app/jobs/regular/merge_user.rb:15:in `execute'
/var/www/discourse/app/jobs/base.rb:316:in `block (2 levels) in perform'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/rails_multisite-6.1.0/lib/rails_multisite/connection_management/null_instance.rb:49:in `with_connection'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/rails_multisite-6.1.0/lib/rails_multisite/connection_management.rb:21:in `with_connection'
/var/www/discourse/app/jobs/base.rb:303:in `block in perform'
/var/www/discourse/app/jobs/base.rb:299:in `each'
/var/www/discourse/app/jobs/base.rb:299:in `perform'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:220:in `execute_job'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:185:in `block (4 levels) in process'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/middleware/chain.rb:180:in `traverse'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/middleware/chain.rb:183:in `block in traverse'
/var/www/discourse/lib/sidekiq/discourse_event.rb:6:in `call'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/middleware/chain.rb:182:in `traverse'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/middleware/chain.rb:183:in `block in traverse'
/var/www/discourse/lib/sidekiq/pausable.rb:131:in `call'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/middleware/chain.rb:182:in `traverse'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/middleware/chain.rb:183:in `block in traverse'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/job/interrupt_handler.rb:9:in `call'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/middleware/chain.rb:182:in `traverse'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/middleware/chain.rb:183:in `block in traverse'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/metrics/tracking.rb:26:in `track'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/metrics/tracking.rb:134:in `call'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/middleware/chain.rb:182:in `traverse'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/middleware/chain.rb:173:in `invoke'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:184:in `block (3 levels) in process'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:145:in `block (6 levels) in dispatch'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/job_retry.rb:118:in `local'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:144:in `block (5 levels) in dispatch'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/config.rb:39:in `block in <class:Config>'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:139:in `block (4 levels) in dispatch'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:281:in `stats'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:134:in `block (3 levels) in dispatch'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/job_logger.rb:15:in `call'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:133:in `block (2 levels) in dispatch'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/job_retry.rb:85:in `global'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:132:in `block in dispatch'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/job_logger.rb:40:in `prepare'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:131:in `dispatch'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:183:in `block (2 levels) in process'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:182:in `handle_interrupt'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:182:in `block in process'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:181:in `handle_interrupt'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:181:in `process'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:86:in `process_one'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/processor.rb:76:in `run'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/component.rb:10:in `watchdog'
/var/www/discourse/vendor/bundle/ruby/3.3.0/gems/sidekiq-7.3.9/lib/sidekiq/component.rb:19:in `block in safe_thread'
以及类似的环境信息：
hostname [...]
process_id 701
application_version 3146142c2ed2c880d53b2f8c136af9f46df99b59
current_db default
current_hostname forum.arduino.cc
job Jobs::MergeUser
problem_db default
time 8:15 am
opts
user_id 42
target_user_id 123
current_user_id 456
current_site_id default
我最终确定，导致卡顿的原因是“来自”用户账户拥有“孤立”的帖子。所谓“孤立”，是指数据库中存在帖子的条目，但与该帖子关联的主题（topic）没有条目。
您可以通过运行以下 Data Explorer 查询来检查给定用户账户中是否存在“孤立帖子”：
-- [params]
-- integer :user_id
SELECT
posts.id,
posts.topic_id
FROM
posts
WHERE
posts.user_id = :user_id
AND posts.topic_id NOT IN (
SELECT
topics.id
FROM
topics
)
在从数据库中删除孤立帖子后（感谢 Discourse 团队的协助，因为我们使用的是 托管计划），我成功地完成了账户合并操作。