Hello,
Below SAP note explains the cause and the solution,
1753711 - Error message HUGENERAL327 comes in VL09 when HU unique flag is not set - workaround
1993159 - VL09: fails with error message HUGENERAL 327
You need to implement the notes to have the issue solved.
Please check and confirm if they help you 
Best Regards,
Ameya B.