Not sure who exactly you have been dealing with for the month with Xerox but the issue is 100% known in the specific firmware on the 5955, and the firmware on the other 2 are way older than 2nd level would even troubleshoot at this point just due to the amount of fixes to scan that have been added in the 18 newer releases for the 7970 and 19 newer for the 7855.
As for which version you should be running, as of today, the current for all 3 devices is 073.xxx.008.05210
The tool install method should be used for all 3, or an Altboot, do not update direct from a 072 release to an 073 release using the CWIS method.
Once you update they will probably just work, but if they don't, you can enable Network traces and see the whole communication via Wireshark
CWIS > Properties > Security > Logs > Network Troubleshooting
Latest firmware
And as for knowing what firmware is the latest, Xerox uses formatting that can be decoded if you know what to look at, and the following is just what to look at.
