Backup2 fails randomly because can't find the backup path

[didix21]

The problems seems to be originated when moving from v8:string to c string. The following error appears:

node(43523,0x106c30580) malloc: Heap corruption detected, free list is damaged at 0x6000036b5040
*** Incorrect guard value: 208739339796592
node(43523,0x106c30580) malloc: *** set a breakpoint in malloc_error_break to debug