I'm playing with the mod https://mods.factorio.com/mod/calcite-casting and while it does add the "Steel with Calcite" to the default "Steel Productivity" research, it is also creating it's own "Steel Productivity" with just itself. And these stack, so having 2 levels of each researched gives Steel With Calcite a 40% total bonus.

If a recipe is already included in an existing productivity research, it should be ignored by my mod. On my end, calcite casting is added as a separate research, but not twice. I'll see if I can add some logic to recognize that it could be added to the existing research instead.

This should now work in 1.3.7. Let me know if you encounter further issues.

Seems to be fixed. I only see one Steel Prod research now. Thank you.