HI Massimo
in order to solve many issues in LMDB try this way:
Go to SA38.
Run program "RTCCTOOL".
The program show you some recommendation " mostly sap notes" you need to implement to solve many problems. Do not forget that this program use SapNet account to connect to sap service and provide solution for you. In your case this is extremely possible that system ask you to upgrade your ST-PI and ST/PI-A to the latest version and install some patches.
Regards,
ALI.