Over the past few years I've noticed and issue with the lengths of some of the larger plates. I first noticed this with the solar panel 'wings' on the droid TIE fighter from the TIE Collection. The large, 4x8 (10?) plates, when placed end to end, were about 3/64ths longer than the blue 1x8 tiles used to hold them together. While this isn't really a huge deal, it causes the panels to bow outward and just doesn't look very good.
I've had this problem come up a few other times as well, but it wasn't anything a bit of 220 grit sand paper couldn't fix.
While tinkering last night, I noticed another issue with a handful of these pieces. When compared, 3 of the five pairs I checked had the left one longer than the right one by close to 1/16th.
While the problems are relatively minor, when added, they could prove to be a larger issue.