**The herbs and pepper are very unlikely to have supplied enough oil to keep 12 ounces of butterfat liquid.** Your intuition about the quantities is sound. Poor straining might leave flecks or sediment, but it would not normally prevent the fat from setting.

The more likely explanation is **delayed crystallization after melting**. Butterfat contains a mixture of fats that crystallize at different temperatures. Fully melting it destroys its existing crystal structure; cooling it back to a temperature where solid butter normally holds its shape does not necessarily make it firm immediately. Cooling rate and time affect how those crystals reform. That makes crystallization a plausible explanation for your batch, although the exact temperature and cooling time would be needed to establish it. [Research on butterfat crystallization](https://pubmed.ncbi.nlm.nih.gov/15653516/)

Try refrigerating a small portion for several hours, or overnight. It should become firm; then bring it back to kitchen temperature and see how it behaves. If it sets in the fridge, the problem was most likely its cooling history or temperature. If the **fat itself** remains liquid after overnight refrigeration, that would be unusual for clarified butter and would suggest substantial added liquid oil or a butter blend.

Fresh herbs can also introduce water. That may leave a separate liquid layer beneath the solidified fat, but it does not mean the butterfat failed to set.