Les:
LED displays in Classics (as you may have noticed) consist in three modules of five digits each, each module in a dual-in-line IC package, but molded in a transparent red plastic, and with individual dome lens molded above each digit. I suppose that a mechanical misalignment is unlikely, because the holes on the printed circuit board contribute to the inter-module alignment. There may be a height misalignment if the module was not properly seated while soldering, and that may cause some optical/visual shift, but I don't think of it as likely, either. And, in the event of a misalignment, it surely will affect all the digits of the block (1 to 5, 6 to 10, 11 to 15). If you unit has been repaired, there may be a chance of inaccurate placement or seating of the middle module, just a guess...
The modules were sorted by brightness by HP Optoelectronics Division at production time (the same modules were available as an electronic component for other manufacturers to buy). There was a letter suffix to identify the relative brightness, and care was taken so the three modules in any given calculator have the same brightness category. Again, a repair work may have used different brightness group, perhaps that may cause an apparent visual shift.
Just some ideas, hope it helps.