Submit form ended to 'expected string or buffer'

[ntmlod]

I have edit my form several times because in the beginning I wasn't not sure if I had followed the good method to implement it (more than one {{{#!WikiForms }}} in the page, issue with void value at submission).

I have simplified my initial form in order for testing.

{{{#!WikiForms
<tf>submit:label='Record your changes'</tf>
<tf>lastmodified</tf>
<tf>dump:.*</tf>
{{{#!td
1
}}}
{{{#!td
<tf>input:1_revision</tf>
}}}
{{{#!td
<tf>select:1_arch:'' 'select 1' 'select 2'</tf>
}}}
{{{#!td
<tf>input:1_compile</tf>
}}}
{{{#!td
<tf>textarea:1_report</tf>
}}}
{{{#!td
<tf>textarea:1_comments</tf>
}}}
{{{#!td
''<tf>when:1_revision</tf>'' \\by __<tf>who:1_revision</tf>__
}}}
|-
{{{#!td
2
}}}
{{{#!td
<tf>input:2_revision</tf>
}}}
{{{#!td
<tf>select:2_arch:'' 'select 1' 'select 2'</tf>
}}}
{{{#!td
<tf>input:2_compile</tf>
}}}
{{{#!td
<tf>textarea:2_report</tf>
}}}
{{{#!td
<tf>textarea:2_comments</tf>
}}}
{{{#!td
''<tf>when:2_revision</tf>'' \\by __<tf>who:2_revision</tf>__
}}}
}}}

When I submit some fake values, I get the error message on /wikiforms/update but regarding the database the process seems to have crashed in the line 2 with missing records.

I have nothing in the Trac log and I assume the message comes from the Apache server because the pattern is unusual.