Maybe related? There is this recurring error in the logs:
Job exception: undefined method `name' for an instance of String
/var/www/discourse/app/models/topic_embed.rb:125:in `map'
/var/www/discourse/app/models/topic_embed.rb:125:in `import'
/var/www/discourse/plugins/discourse-rss-polling/app/jobs/jobs/discourse_rss_polling/poll_feed.rb:52:in `block in poll_feed'
/var/www/discourse/plugins/discourse-rss-polling/app/jobs/jobs/discourse_rss_polling/poll_feed.rb:41:in `each'
/var/www/discourse/plugins/discourse-rss-polling/app/jobs/jobs/discourse_rss_polling/poll_feed.rb:41:in `poll_feed'
/var/www/discourse/plugins/discourse-rss-polling/app/jobs/jobs/discourse_rss_polling/poll_feed.rb:20:in `execute'
/var/www/discourse/app/jobs/base.rb:305:in `block (2 levels) in perform'
rails_multisite-6.0.0/lib/rails_multisite/connection_management/null_instance.rb:49:in `with_connection'
rails_multisite-6.0.0/lib/rails_multisite/connection_management.rb:21:in `with_connection'
/var/www/discourse/app/jobs/base.rb:292:in `block in perform'
/var/www/discourse/app/jobs/base.rb:288:in `each'
/var/www/discourse/app/jobs/base.rb:288:in `perform'
sidekiq-6.5.12/lib/sidekiq/processor.rb:202:in `execute_job'
sidekiq-6.5.12/lib/sidekiq/processor.rb:170:in `block (2 levels) in process'
sidekiq-6.5.12/lib/sidekiq/middleware/chain.rb:177:in `block in invoke'
/var/www/discourse/lib/sidekiq/pausable.rb:132:in `call'
sidekiq-6.5.12/lib/sidekiq/middleware/chain.rb:179:in `block in invoke'
sidekiq-6.5.12/lib/sidekiq/middleware/chain.rb:182:in `invoke'
sidekiq-6.5.12/lib/sidekiq/processor.rb:169:in `block in process'
sidekiq-6.5.12/lib/sidekiq/processor.rb:136:in `block (6 levels) in dispatch'
sidekiq-6.5.12/lib/sidekiq/job_retry.rb:113:in `local'
sidekiq-6.5.12/lib/sidekiq/processor.rb:135:in `block (5 levels) in dispatch'
sidekiq-6.5.12/lib/sidekiq.rb:44:in `block in <module:Sidekiq>'
sidekiq-6.5.12/lib/sidekiq/processor.rb:131:in `block (4 levels) in dispatch'
sidekiq-6.5.12/lib/sidekiq/processor.rb:263:in `stats'
sidekiq-6.5.12/lib/sidekiq/processor.rb:126:in `block (3 levels) in dispatch'
sidekiq-6.5.12/lib/sidekiq/job_logger.rb:13:in `call'
sidekiq-6.5.12/lib/sidekiq/processor.rb:125:in `block (2 levels) in dispatch'
sidekiq-6.5.12/lib/sidekiq/job_retry.rb:80:in `global'
sidekiq-6.5.12/lib/sidekiq/processor.rb:124:in `block in dispatch'
sidekiq-6.5.12/lib/sidekiq/job_logger.rb:39:in `prepare'
sidekiq-6.5.12/lib/sidekiq/processor.rb:123:in `dispatch'
sidekiq-6.5.12/lib/sidekiq/processor.rb:168:in `process'
sidekiq-6.5.12/lib/sidekiq/processor.rb:78:in `process_one'
sidekiq-6.5.12/lib/sidekiq/processor.rb:68:in `run'
sidekiq-6.5.12/lib/sidekiq/component.rb:8:in `watchdog'
sidekiq-6.5.12/lib/sidekiq/component.rb:17:in `block in safe_thread'