. . . of the leading and trailing date rings has been reported in the past. It's not a common occurrence, and I've never seen it personally, but problems can crop up with any mechanical device, and the PanoDate complication is no exception to the rule. For what it's worth, some of the images I've seen that depict a noticeable misalignment are tolerable; if memory serves correctly, there was only one sample where the misalignment was so obvious that correction by the service department was mandatory, and that was with a cal 39 perpetual calendar.
Unless the model you're considering is one of the last models still available from an authorized dealer, it's likely that the watch is out of warranty, so it would have to be returned to G O for correction. They might recommend a complete service, so it would be advisable to take that contingency into consideration when making an offer on the watch.
Hope to see the PanoGraph on your wrist soon!
Cordially, Art