Probably, the problem is in the NaviServer 4.99.31 release. The newest NaviServer 4.99.* releases are essentially backports of bug fixes from NaviServer 5. These versions are less extensively tested compared with NaviServer 5.
I have downgraded a few weeks ago the default install from NaviServer 4.99.31 to 4.99.30 due to a bug-report with spooled forms (typically file uploaded via from), which is fixed in the newest (unreleased) version of the NaviServer 4.99 release branch.
