I can send the same print job 10 times and it will only print 1 mabye 2, they others are displayed as Unknown, please see the below image.
I have tried several, drivers, machines, operating systems, printed directly to the printer over the network, via a print server and its still the same.
I had one doing this resetting fiery back to factory settings and then putting back the IP fixed this
Change the Protocol from "RAW" to "LPR" and name to "print". This a bug with the RAW protocols.