Hello,
Enable the 'flow debugs' as below:
set ff src-ip 192.168.42.x dst-ip 172.20.0.y (or any test PC IPs)
set ff src-ip 172.20.0.y dst-ip 192.168.42.x
set db size 4096
debug flow basic
Now initiate the file transfer between above two IPs and once it fails, stop the debugs with 'undebug all' and attach the output of 'get db stream' so that we can have a look.
Regards,
Rushi