Hello Miquel,
Unfortunately there are no commands to check port congestion or buffering with the SecureStacks.
There are a few things ti understand about pauseframes and end stations and clients:
1. The end station or switch will send pauseframes when it being overwhelmed with traffic that it should not see could be:
A. Misconfiguration of a switch or switches.
B. Low end pc's
C. Misconfigured NIC
The biggest thing to look into what ports are sending in the pauseframes and run a sniffer on the port and verify that it should be seeing the traffic and if not then look into the configuration.
I always look to see if the up link ports are either sending or receiving pauseframes and then check the switches that are connected and look at the show port flowcontrol ports and check the TX counters are incrementing.
If you would like help with this issue then please contact the GTAC to open a ticket and i will be glad to assist in isolating your issue.
Jason