When paracelsin is installed, Cerys' nitric acid production recipe produces integrated nitric acid(paracelsin's nitric acid icon)
But processing unit production recipe(processing unit from nitric acid) requires Cerys' nitric acid.

As a result, the processing unit could not be created in Cerys.
Other recipes for Cerys that require nitric acid work normally.(ex : overclock module)

Are there any other mods that modify that recipe after my mod? The way I do the patching is mod-agnostic, and the only way I can think of for that to happen would be for another mod to change things after I do.

You can check for this by looking at the mod list in Factoriopedia for the recipe.

EDIT: Looks like this is a compatibility issue with xyrc's mod. If you use their rebalance setting, it loads after mine and reverts it back to kr-nitric-acid. Unfortunate there's nothing I can really do there. Their patch will need to take into account mine's fluid standardization.

I think that's right

I submitted a PR which was accepted. Should be fixed in the next version of xyrc's mod.