I have habitually in exporting from Lightroom 4.4 used the dropdown renaming choice "custom name - original file number" and my entire library uses custom names I have devised with the original file number which also checks with the RAW filename. Suddenly about 2 weeks ago this feature did not work, defaulting to the custom name and a number sequence unrelated to the original file number.
Seeing that LR 6 is available as a stand alone, I purchased it a couple of days ago supposing this would correct the problem. But the SAME dysfunction continues. It is as though whatever went wrong with version 4 has been picked up by version 6 during installation.
I have reset Export function to factory defaults, reviewed Edit..Preferences, finding nothing to change, and installed today's update to LR6. Same problem.
Please advise how to correct this so that this renaming choice, which occurs in ANY export dialog, including file renaming BEFORE export, does its job.
Last February this forum shows a thread between Adobe and RichardC who seemed to have the same or a similar problem. The thread ends with his writing "that worked, thanks" but I could not find any message detailing what he did to make it work correctly.