Random error when import file in update_cache

[polargeex]

Completed 500 Internal Server Error in 429ms (ActiveRecord: 57.3ms)

TypeError (can't dump hash with default proc):
plugins/msproject_import/app/controllers/msproj_imp_controller.rb:328:in update_cache' plugins/msproject_import/app/controllers/msproj_imp_controller.rb:382:in import'
plugins/msproject_import/app/controllers/msproj_imp_controller.rb:256:in block in process_tasks' plugins/msproject_import/app/controllers/msproj_imp_controller.rb:248:in each'
plugins/msproject_import/app/controllers/msproj_imp_controller.rb:248:in process_tasks' plugins/msproject_import/app/controllers/msproj_imp_controller.rb:42:in run'
lib/redmine/sudo_mode.rb:63:in `sudo_mode'

It's strange because this error don't occur when we put import in parent ticket

Projet.zip
Redmin 3.2.3 with mysql
Debian 8
Rails 4.2.5.2
ruby 2.3.4p301 (2017-03-30 revision 58214) [x86_64-linux]