I use NBAR for Citrix packet type classification (to also distinguish between screen packet and printing or disk copying packets). I have not, though, confirmed that all packets are properly being matched. I've only noticed that NBAR "sees" some different Citrix packets.
I believe I recall, though, that the Citrix subtype was a later addition to their protocol, so if there were any earlier Citrix protocol packets, NBAR would then be unable to distinguish the kind of Citrix traffic. (I'm not current on Citrix platforms, would assume "Citrix 4.5" would use the later Citrix protocol.)
I also recall(?), Citrix NBAR subtype matching is only present in later NBAR variants. If correct, you might want to confirm what NBAR Citrix version is being used. (NB: also recall, there were NBAR PDLMs for earlier IOSs, but shouldn't be necessary in later IOSs.)
So to summarized the last two points, confirm all your Citrix packets do contain the subtype marking and that your using the latest Citrix NBAR protocol matching version.
PS:
If you resolve or discover the cause of this issue, please post a follow-up.