I suggested you update because you are using an old version.
There is a chance that the update will fix your problem.
We had a similar problem before.
Our solution method:
We deleted the “submissionChecklist” lines in the “journall_settings” table in the database.
We recreated the Checklists for both languages from the OJS management panel.
This is how our problem was solved.
Please do not forget to backup your database before doing these operations.
So that we can assist you further
Can you check the error log on your server for the domain that used by the OJS?
And paste the related error here so the community can help you with that.