N2000 - Error on stack

Hi, 

I have a configuration of 6x N2000 switches in a stack. 

Management Standby Preconfig Plugged-in Switch Code
SW Status Status Model ID Model ID Status Version
--- ---------- --------- ------------- ------------- ------------- -----------
1 Mgmt Sw N2048 N2048 OK 6.3.1.11
2 Stack Mbr N2048 N2048 OK 6.3.1.11
3 Stack Mbr N2048P N2048P OK 6.3.1.11
4 Stack Mbr N2048 N2048 OK 6.3.1.11
5 Stack Mbr Oper Stby N2048 N2048 OK 6.3.1.11
6 Stack Mbr N2048 N2048 OK 6.3.1.11

I am getting the following error message in log:

 STACKING[spmTask]: spm.c(1431) 3983887 %% Errors detected on stack-port 4/0/51 (oldRxErrors = 7901 currentRxErrors = 7902 oldTxErrors = 0 currentTxErrors = 0). Use the stacking diagnostics command to look at detailed statistics.

show switch stack-ports:

Configured Running Link Link Admin
Interface Stack Mode Stack Mode Status Speed (Gb/s) Status
--------- ---------- ---------- ------------ ------------ ------------
Tw1/0/1 Stack Stack Link Up 21 Enabled
Tw1/0/2 Stack Stack Link Up 21 Enabled
Tw2/0/1 Stack Stack Link Up 21 Enabled
Tw2/0/2 Stack Stack Link Up 21 Enabled
Tw3/0/1 Stack Stack Link Up 21 Enabled
Tw3/0/2 Stack Stack Link Up 21 Enabled
Tw4/0/1 Stack Stack Link Up 21 Enabled
Tw4/0/2 Stack Stack Link Up 21 Enabled
Tw5/0/1 Stack Stack Link Up 21 Enabled
Tw5/0/2 Stack Stack Link Up 21 Enabled
Tw6/0/1 Stack Stack Link Up 21 Enabled
Tw6/0/2 Stack Stack Link Up 21 Enabled

show switch stack-ports diag

Legend:

RBYT : Received Bytes RPKT : Received Packets
TBYT : Transmitted Bytes TPKT : Transmitted Packets
RFCS : Received Frame Check Sequence Errors RFRG : Received Fragment Errors
RJBR : Received Jabber Errors RUNT : Received Packets with size 2 to 63 bytes
RUND : Received Undersize Packets ROVR : Received Oversize Packets
TFCS : Transmit Frame Check Sequence Errors TERR : Transmit Errors

Tw1/0/1
RBYT:2067392660 RPKT:1018030822 TBYT:1626517552 TPKT:1636094788
RFCS:0 RFRG:0 RJBR:0 RUND:0 RUNT:0
TFCS:0 TERR:0

Tw1/0/2
RBYT:978437601 RPKT:354770589 TBYT:3413504613 TPKT:732116527
RFCS:0 RFRG:0 RJBR:0 RUND:0 RUNT:0
TFCS:0 TERR:0

Tw2/0/1
RBYT:3267245986 RPKT:913420270 TBYT:2411587306 TPKT:1363390881
RFCS:0 RFRG:0 RJBR:0 RUND:0 RUNT:0
TFCS:0 TERR:0

Tw2/0/2
RBYT:1626503151 RPKT:1636094755 TBYT:2067389960 TPKT:1018030802
RFCS:0 RFRG:0 RJBR:0 RUND:0 RUNT:0
TFCS:0 TERR:0

Tw3/0/1
RBYT:137797844 RPKT:318199 TBYT:159628879 TPKT:328266
RFCS:0 RFRG:0 RJBR:0 RUND:0 RUNT:0
TFCS:0 TERR:0

Tw3/0/2
RBYT:3209423586 RPKT:25570779 TBYT:3476348880 TPKT:13298182
RFCS:0 RFRG:0 RJBR:0 RUND:0 RUNT:0
TFCS:0 TERR:0

Tw4/0/1
RBYT:506148631 RPKT:309325454 TBYT:1896612193 TPKT:129695115
RFCS:7446 RFRG:457 RJBR:0 RUND:0 RUNT:891
TFCS:0 TERR:0

Tw4/0/2
RBYT:2324266340 RPKT:13285732 TBYT:1457555961 TPKT:13131801
RFCS:0 RFRG:0 RJBR:0 RUND:0 RUNT:0
TFCS:0 TERR:0

Tw5/0/1
RBYT:71936598 RPKT:471683207 TBYT:4278694826 TPKT:218883951
RFCS:0 RFRG:0 RJBR:0 RUND:0 RUNT:0
TFCS:0 TERR:0

Tw5/0/2
RBYT:1896501795 RPKT:129694997 TBYT:512223626 TPKT:309326433
RFCS:0 RFRG:0 RJBR:0 RUND:0 RUNT:0
TFCS:0 TERR:0

Tw6/0/1
RBYT:3413857278 RPKT:732116927 TBYT:978761844 TPKT:354770941
RFCS:0 RFRG:0 RJBR:0 RUND:0 RUNT:0
TFCS:0 TERR:0

Tw6/0/2
RBYT:4278908978 RPKT:218884169 TBYT:72163902 TPKT:471683457
RFCS:0 RFRG:0 RJBR:0 RUND:0 RUNT:0
TFCS:0 TERR:0

So I am having trouble locating what stack-cable is having the problem.
Or does stack-port 4/0/51 point me in the right direction? 
As I understand all the switches has two stack ports on the back, port 1 and 2. 

Of course, Our first step will be to upgrade to latest firmware during next maintenance window,
but I was wondering if I schould replace a stack cable at the same time.