Default EFS corrupetd: can't restore backupped folder

It seems that, for somehwat reason, my IMEI corrupted after switching back from TMo UK to my italian carrier. I couldn't connect to the radio right after having landed.
I did a backup of EFS folder about 1 year ago.
However, copyng nv_data.bin and imei folder from the backup to /efs folder, and changing the permissions (chown set to "radio"), didn't work.
I still get "baseband unknown" and no IMEI.
I tried using Root Explorer and adb: the result is the same.
What am I missing?
Thanks in advance
Device: Samsung S4mini (i9195 - TPH no brand)
ROM: Stock 4.2.2 - Modem: ML4 - Kernel: Stock
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