I use nginx server.
log:
Completed 500 Internal Server Error in 51113ms (ActiveRecord: 51068.8ms)

ActiveRecord::StatementInvalid (Mysql2::Error: Lock wait timeout exceeded; try restarting transaction: UPDATE issues SET issues.status_id = 3, issues.updated_on = '2017-05-18 11:02:23', issues.lock_version = 2 WHERE issues.id = 21991 AND issues.lock_version = 1):
app/models/issue.rb:182:in create_or_update'
app/controllers/issues_controller.rb:499:inblock in save_issue_with_child_records'
app/controllers/issues_controller.rb:487:in save_issue_with_child_records'
app/controllers/issues_controller.rb:185:inupdate'
lib/redmine/sudo_mode.rb:63:in `sudo_mode'