After getting QTR properly installed, I made a few prints. For moderate size prints, all went nicely. Then I tried to make a big one, and this is the result:
It isn’t a one-off, as this one is actually the second one that had this kind of a buffer problem.
Environment: iMac running High Sierra, Lightroom 6.14 perpetual, QTR 2.7.8, 9900-Pro-K4. Printer is still attached via USB, although that will change shortly. The first print that did this was sourced from a 140mp file produced by Photoshop. At first I thought that the problem might be due to simply having too big an input, since 140mp is definitely not your garden-variety file, even if a few cameras do produce such things. However, the one shown above is a straight print of a 36mp D810 file, so that doesn’t seem to be the item in play.
In the case of this particular print, the paper moved through the printer with what is shown as the right hand side leading through the printer (i.e., physically down on a 9900). The erroneous part of the print came out first.
At this point I have no idea where this error even occurred. It could be in Lightroom (6.14 does not have an admirable stability record), it could be in QTR, I suppose it’s even possible that it’s in the MacOS print spooler, and I could imagine ways in which the printer might do this too. Short of playing binary search by changing out each of the components, how could I diagnose this? And how can I avoid it?