Solution : https://service.sap.com/sap/support/notes/362064 (SAP Service marketplace login required)
Key words :
include na_allg_noverarbeitung object doku id txu1, select 'edit -> maintain selected messages', attached source code corrections, enter message class 'cj', system displays error message00347, standard setting 'display field', input fieldthe long text, select 'long text', additional key words, u1 system response/