Redmine

We currently have the following environment:

Environment:
  Redmine version                2.3.4.stable
  Ruby version                   1.9.3-p484 (2013-11-22) [x86_64-linux]
  Rails version                  3.2.13
  Environment                    production
  Database adapter               SQLite

We are trying to upgrade to:

Environment:
  Redmine version                3.2.0.stable
  Ruby version                   2.2.1-p85 (2015-02-26) [x86_64-linux]
  Rails version                  4.2.5
  Environment                    production
  Database adapter               SQLite

We are using thin as server.
We have the following issue:

Roles different to manager or users without Admin permission can't see any issue on the list.
They can access the issues directly (knowing the link).
I tried changing the role permission for "issues visibility" and if set to:

• all issues: it works ok, the user can see all issues.
• all non-private issues: doesn't work, the user can't see any issue.
• issues created by or assigned to: doesn't work either. I also tried creating an issue and assigning it to the same user, and that user still can't see it.

I compared Roles & permissions and they seem to be ok.

Also tried 3.1.3, with the same luck.
We are using some plugins, not sure if that can be related.

Any ideas of what may be going on here and how to solve it?

Thanks.