I've noticed in several situations that stacks are much slower to respond to snmp and you can even tell things are sluggish when you are ssh'd in and try to run commands.
You should check the cpu usage to make sure things aren't being affected by high cpu.
Also, how many uplinks do you have leaving that stack? Are they port channeled? I'm wondering because with 9 switches in a stack, it would seem you could overwhelm your uplink port.
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