I've been using a digital camera with Lightroom and Negative Lab Pro to digitise my collection of 35mm negatives.
I discovered about a year ago that flat field correction is an essential part of film digitization, since no lens/light combination is ever going to be 100% even.
The issue is that flat field correction, after many years, remains buggy. About 10% of my conversions contain strange blotches that aren't visible on either the negative or blank plate. A further 10% become very overexposed and washed out looking. I'm finding that these problems occur within batches rather than individual photos - if one image has an issue, it is likely that all other images corrected with it will contain the same problem.
This is even more annoying since I'm setting FFC to automatically delete the original RAW files upon correction, since I've backed them up separately and wish to save space on my PC. So if a correction fails, I have to manually retrieve the files from a backup drive to reattempt it (note that I have 450 rolls of digitized film, or 16,000 photos, so this is my only option).
The only way that I can get more reliable results is to perform corrections in smaller batches (i.e. 5-10 photos at a time instead of 30-40). This makes no sense though, since LR should be correcting every photo individually in relation to the blank plate, the correction of one photo should have no impact on that of another.
It's also worth noting that I've been experiencing this problem on both Mac and PC over the course of the last 2 years.
This is quite annoying since FFC correction is a powerful tool with spotty implementation - I'm hoping Adobe can find a fix to make it more reliable in the near future.
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