Solution : https://service.sap.com/sap/support/notes/313683 (SAP Service marketplace login required)
Key words : 
system generates error message gu506, year-dependent fiscal year variant, additional key words gu 506, fiscal year variant &, shortened fiscal year, attached advance corrections, program error, actual postings, activity allocation, posting period &
Related Notes : 
       
| 672255 | Shortened fiscal year/changing fiscal periods |