Hard Candy - when to add tincture?

Greetings, fellow edible enthusiasts!

I've been working on recipes for various candies (everyone needs a pandemic hobby, right?), and have had issues with hard candy. I prefer recipes without corn syrup, so if you're going to post a recipe in response just please bear that in mind. It seems like every time I go to add the tincture at the end (pulling the candy off the heat at 300 degrees, adding food coloring and tincture), the whole candy mess seizes and I can't pour it into molds. I thought maybe it was the temp difference of storing the tincture in the freezer, so allowed it to come to room temp before making candy with same results. I'm afraid to add the tincture before bringing to 300 degrees to avoid degradation - any thoughts/tips on that? Or do I let it cool down to a certain temp before adding? But I also still want it to be workable to pour into molds. Halps, please! TIA!

Use a jello pack once you get sugar and syrup mixture to 300 for flavoring and to harden candy. Put tincture in the jello mix.
Search up cannabis hard candy on YouTube and you can find the reciepe

citric acid helps with crystallization, is there citric acid in the recipe? you could also add cannabutter and a little sunflower lecithin at the beginning. Folks bake at 350 all the time, 300 with the fat protecting the THC should be fine I’d think.