Its administratively set to 1500, but it is operating at 9000. What does the rest of the port channel look like? You may need to pull your ports out of the ifgrp, net port mod -mtu-admin <desired value> then add them back to the ifgrp. Then add the ifgrp to a broadcast domain. MTU is managed at the broadcast domain level, and all ports within a broadcast domain must have the same MTU.
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