AssocationTypeMismatch when closing issues broken with external issue trackers

https://sentry.gitlap.com/gitlab/gitlabcom/issues/42537/

ActiveRecord::AssociationTypeMismatch: Issue(#70249866447980) expected, got ExternalIssue(#70249796695680)
  lib/gitlab/database/load_balancing/connection_proxy.rb:75:in `block in write_using_load_balancer'
    connection.send(name, *args, &block)
  lib/gitlab/database/load_balancing/load_balancer.rb:66:in `block in read_write'
    yield ActiveRecord::Base.connection
  lib/gitlab/database/load_balancing/load_balancer.rb:116:in `retry_with_backoff'
    return yield
  lib/gitlab/database/load_balancing/load_balancer.rb:65:in `read_write'
    retry_with_backoff do
  lib/gitlab/database/load_balancing/connection_proxy.rb:69:in `write_using_load_balancer'
    result = @load_balancer.read_write do |connection|
...
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ActiveRecord::AssociationTypeMismatch: Issue(#70249866447980) expected, got ExternalIssue(#70249796695680)