Hi Stanley,
I work for NetApp doing consulting on system deployment.
A few commands you should use to troubleshoot this, I infer you are using 7-mode since you mention the ifgrp status command.
1. CDP command can help totally validate which network switch ports are in use. Make sure it is on, and then use CDP to show neighbors.
ps7mode1> options cdpd
cdpd.enable on (value might be overwritten in takeover)
cdpd.holdtime 180 (value might be overwritten in takeover)
cdpd.interval 60 (value might be overwritten in takeover)
ps7mode1>
ps7mode1> cdpd show-neighbors -v
Remote Device: phx-5k(SSI132908XB)
Local Port: e0a
Holdtime: 166
Capabilities: Switch, IGMP
Platform: N5K-C5010P-BF
Remote Port: Ethernet120/1/25
2. Ifstat command is what you want to use to understand individual Ethernet port usage and frame counts. Use ifstat against the two members of your ifgrp and see if one has more traffic than another. If you like you can clear the existing counters with "ifstat -z", just make sure to record the pre-cleared statistics prior to doing so.
I do find it odd that the link light stayed on when you pulled the cable, and I suspect that'd be the only reason Support went down the road of trying to swap the specific physical interface. I like the idea of checking the SFP as well.
In my travels, lag_inactive *always* ended up as a mis-configuration or mis-communication as to which ports are involved in the LAG. If the port is suspended on your network side, confirm the cabled port with CDPD and then have them unsuspend it (up-up it), and see if the port-channel goes live on all member ports.
Cheers,
Hadrian