RTRR problem - Can't get the information of the source (-62)

[ken_nx]

2 QNAP NAS connected via a linksys E3000 router & cat6 cables on same intranet

Source:
TS-470 Pro
4.1.1 Build 20141101
Intranet IP 192.168.1.2, running RTRR server on port 8899
up 24*7

Destination:
TS-212P
4.1.2 Build 20141229
Intranet IP 192.168.1.4, set to auto power-on everyday 0650hr, and synchronize a the folder "homes/SK" of Source everyday 0700hr thru RTRR

But error message
Can't get the information of the source (remote side) directory "homes/SK/La-Ikus/Documents/"! (-62)
Connection timed out, bad networking quality or the server connection closed unexpectedly!


It is mysterious that it is successful if i create another job and just synchronize the folder homes/SK/La-Ikus/Documents/". but fail for the mother directory
I have tried created another folder with similar name and move the files to new folder, also fail

please help, thanks



Error log
[2015/01/23 10:31:06] # ERROR: Can't get the information of the source (remote side) directory "homes/SK/La-Ikus/Documents/"! (-62)
[2015/01/23 10:31:08] The synchronization stopped with errors.
[2015/01/23 10:31:08] Sync statistic: Total number of the folders: 8467. Total number of the files: 224197. Total number of the skipped files: 224187. Total updated size: 2.06 MB. Average updating speed: 1.30 (KB/sec). Time elapsed: 27 minutes 7 seconds
[2015/01/23 10:31:15] Connection timed out, bad networking quality or the server connection closed unexpectedly! Begin the 1st retry.