Sounds pretty odd, Harriis, since error 81 is paper advance, not a carriage problem. If it took care of your problem I guess the error code was erroneous, and fixed is fixed. If, however, you develop problems again you might look here.
On the subject of lubrification (I swear, that's what HP calls it), you would think that it would be a straightforward process for HP to inform its owners how to take care of their printers.
Unfortunately, HP can't even seem to agree from one tech support person to the next as to the exact routine one should follow for lubrication. Users are educating other users instead of HP leading the way themselves. I'm afraid that HP thinks oil sounds messy and un-user friendly, so they try to softpedal the routine maintanence chores like oiling, wiping down the interior of the printer for overspray, and for me, at least, cleaning the printhead contacts for ink overspray as well.
There may be two problems then that need to be documented for Z users, (well all the series then of LFPs with the same chassis).
If the slightest bit of dirt affects the return of the carriage then they will have to take care to put up full instructions on how to do so, and offer an easily accessible lube kit for a moderate price.
BTW if the carriage cannot return then indeed it will block paper advance.
Second will be the build up of ink in the end areas, and in the ink wells which are going to reduce the conductivity of the contacts. I can imagine this will be a simple cleaning procedure, but it would be better if an official procedure was documented.
Where as CAD printers rarely use rag or media where lint is going to wind up in the cavity, photo printers do and will. Users will be happy to do regular maintenance, but they need concise instructions on how to do so.
PS Ron do you have a repair guide?