Solution : https://service.sap.com/sap/support/notes/919907 (SAP Service marketplace login required)
Key words :
'maintain field equi-eqasp' dialog box, eqasp data element, start transaction se11, text language field, 'text language' attribute, eqasp field, equi-eqasp, text language, field information, equi table
Related Notes :
| 1051414 | Table EQUI, IFLOT: Incorrectly set flag 'Text Language' |