Hi Rob,
TCP port 2598 is part of the Citrix optimization policy.
Have you placed your policy in the top, to ensure that it's processed before any default optimization policies ?
Otherwise you risk hitting the default Citrix policy before yours.
Try issuing these commands in both ends :
show class-map type waas Citrix
show class-map type waas <your class-map>
and monitor the flow matches !
Best Regards
Finn