DMS prevents Issue transfer to other project

[vchryssos]

1. Create new Issue in Project A of RM and attach a Document / Submit
2. Edit the Issue and move it to Project B / Submit

Expected result: Issue is transferred to Project B
Actual result: blank screen. Issue is not transferred.

Bug insists even after you delete attached Documents and even after you empty the DMS Trash Can

Environment:
Redmine version 3.4.6.stable
Ruby version 2.4.4-p296 (2018-03-28) [x86_64-linux]
Rails version 4.2.8
Environment production
Database adapter Mysql2