I wonder if it's a security issue. Can the users that cannot see the reports in their own print queue see them if the look at the print queue for the user that actually ran the job that created the report? If not, that might be a clue. It might help to compare the security settings for the one user that can see the reports, and those that can't.
Also, there are other settings that affect report distribution. In addition to distribution groups, there are user groups (usergrpdef) and distribution list groups (dstlstgrpdef), and they all interact if IIRC. I have a few pages of notes on how I untangled that web when we first started with Lawson several years ago. I could email them to you if you like.