Problem

DIAGI=102 and DIAGP=51335237 at the first transfer attempt.

After 15-20 minutes, transfer is restarted and it finishes successfully.

Local Diagnostic Code: 102
Description: File selection error
[Complementary]

SIFM INQ : GET FILE INFO ERROR \\UNC_SRV1\data\TESTING\My_BigFile.tbl

[Protocol]
51335237

Resolution

The error is returned by the system when accessing the UNC path, the error itself stand for:

ERROR_TOO_MANY_SESS
69 (0x45)
The network BIOS session limit was exceeded.

It may be the root cause interrupting CFT from reading the file from that location.

check for too many active sessions to the UNC path.

Check on the server for the list of active sessions on the share when you have the error.

That UNC server maybe be highly solicited?