Getting a prefilebackup script error

Hi,

I have client 2.1.15 installed on a Windows 10 machine. It attempts to run the backup procedure but fails to perform the backup. The server shows in the log:

Errors
04/20/17 13:16
Constructing of filelist of “ins-emt” failed: error - prefilebackup script failed with error code 255
Errors
04/20/17 13:16
Backup had an early error. Deleting partial backup.

I see in the docs that if prefilebackup fails it’ll return a numeric code, but I have no idea what this number represents - does anyone know what this return code is?

Thanks!