sundance-communications.com Forums Telephony Discussion Phone & VoIP Systems Comdial Telephones & Systems MP5000 and fiber expansion card issue

I am having an issue with a cabinet that is linked to the main cabinet via a fiber expansion card. Users that have a phone connected to a station card in the far end cabinet see their displays slowly fade, go blank, then pop up stating "Data Lock" and of course all active calls are cut off. Then after a few seconds the displays go back to normal showing the time, date, vmail, etc and the users can again use their phones. This is happening several times throughout the day. I am able to replicate what the users experience by disconnecting the fiber patch cord from the fiber expansion card.
I have light tested the fiber and even tried moving the connection to other open strands but the issue is still occurring.
The main cabinet also has another cabinet connected to it via a fiber card and the users on that cabinet do not experience the issue. I have looked at the system logs and don't see any reboot events so I'm not sure what else to check. Is this possibly do to a bad fiber card?
Has anyone else experienced such an issue with fiber cards and or have any solutions.
Thanks in advance for any assistance.

I've never had a fiber card go bad...only the fiber feed itself. I'd roll fiber cards with the two cabinets and see if the problem follows the cards or stays isolated to the cabinet with the current problems. Also turn on Blackbox if it is at a high enough software level so the tech support people can see what is happening.