I think you have answered this question for your self without realizing it. As you say on a Test Page it prints properly but the thing doesn't work quite right when used from a PC. As the imagining process is working perfectly on the Test Page the problem has to be in the Circuit Board that Interfaces between the PC and the printer internals.
While it could just be a bad connection with the printer lead I would imagine that has been changed already so I would tend to rule that out. Short of replacing the board you'll have to pull it out check all the solder joints for a Dry Joint where contact isn't being made properly and re solder the joint with the correct Soldering Iron {I know it sounds obvious but I've seen many people use the wrong tools for a job so I never ever say just do this or that and it might be fixed on one occasion I saw a Circuit Board that the person had replaced a resistor with a plumbers Soldering torch and burnt the board to bits so don't take it personally.}
Good luck if you can not find either a bad connection on the socket or a bad solder joint as if Kyocera is anything over where you are like they are here it will work out far cheaper to buy a new unit and they is before you even consider your labor, they drive me nuts with their constant delays and assorted problems that they produce. I once waited 3 months and several trips down to a new unit that had A4 & A3 paper in it and it wouldn't select the right drawer to take the paper from when some forms where being printed out. It was a straight software problem but the people at Kyocera insisted on e-mailing me the fix and after 3 attempts at this all of which took several weeks to arrive and none actually worked I was finally advised to download a patch from their web site. If they had of suggested that first it would have saved me hours and several hundred K's in wasted trips.
Col
