The batch is inconsistent
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Roast drift across a run
An oven or roaster that is not at a steady temperature, batches of different sizes, or trays loaded differently will produce noticeably different color and flavor from the same nominal roast. Buyers notice half a shade, and in this craft the color is the first thing they see.
The nuts changed
Nuts are agricultural and vary by lot, origin and season. The same roast applied to a different lot gives a different result, which is why the lot belongs in the log alongside the roast record. It is also a reason to be careful about blending lots without recording it.
A long grind heats the batch
Friction warms the product, and a batch that finished much warmer than usual fills differently, cools differently in the jar and can set up with a different texture. Measuring the temperature at the end of the grind costs nothing and explains a surprising number of complaints.
Fix the roast first
It is the step where consistency buys the most, and it is the one that also carries the safety control, so tightening it pays twice. A roaster with reliable temperature control is usually the right first equipment purchase for this reason rather than for capacity.
What a buyer will ask
Whether the next delivery will match this one. That is answered from the roast records and the lot history, not from reassurance, and very few small makers can put the numbers on the table.
Check it is really one batch
Before diagnosing anything, confirm the jars came from one run. Stock from two days packed into the same case, or two lots blended without a record, produces exactly this symptom and has nothing to do with the process. The batch code settles it, which is the argument for coding every jar.