Solution : https://service.sap.com/sap/support/notes/970752 (SAP Service marketplace login required)
Key words : 
system issues message sa_diag 013, solution manager diagnostics reason, 'enter server data' screen, st 400 patch level 12, solution manager diagnostics, abap application server, composite sap note, system/main instance &1/&2, detail screen displays, save installation paths
Related Notes : 
       
| 1161294 | Name chg, SAP Solution Manager 4.0 to Solution Manager 7.0 | 
| 971192 | SMSY: Cannot change server role | 
| 970636 | SMSY: Server where-used list with no product/main instance | 
| 940154 | SMSY:Enhanced attributes for hardware instances not possible | 
| 906705 | SOLMAN 4.0 SMD: Error when saving the installation paths |