Fanuc 15 TF SLC error 08 : PC050 & SV013 X improper V-ready off

Hi, we have a problem on a Boehringer lathe machine, with Fanuc 15TF & servo A06B-6058-H005
The machine went down, by restart it gives alarm SLC error 08 : PC050 -> Base 1 ( PMC ) ; 01P1D
Then sometimes the machine goes in error during the time that it stands idle, there's no turning .
Often goes it in error whilst turning .
The error = SV013 X improper V-ready off ; SV013 Z improper V-ready .
By turning off the machine the error doesn't reappear for a while
When this fault appears, I see no red error leds on the servo .
I've allready changed the Base 2 card ( 01P24 ) at the NC .

Any help is welcome