You say the latest firmware, but is it actually? The latest release is 061.121.225.06100 which is 4 full releases newer than the General release posted on Xerox.com.
That release is here , just use WC75xxSpar for the release code.
If that fails, or is what you are currently running anywhere, your best bet is to share the same folder via FTP and have the printer access it that way. This way nothing changes on the client PC side.
What you are seeing is not a normal condition, but it would be very hard to get to the bottom of this as it would make for a very large Wireshark trace.