Depending on the age of the flavors, that could be an issue as well. Some of my older flavors, that came from a shitty vendor with horrible lpde bottles, started to get harsh. I didnt know that at the beginning, but a reason i re bottle everything upon arrival, in most cases. Check that this doesnt apply to you, as well as the date.
If your nicotine is not stirred, or some suggest shaking it, enough this can create hot spots (not just in vg) that can be harsh.
Your setup is another thing that could be a factor, old coils, cotton, too restricted, too much airflow, too hot, too cold yada yada. Some people dont realize that certain profiles can be affected by this. Not every juice works with the same hardware or settings.
You should single flavor test all of them, i personally know that i am very sensitive to certain types of flavors. Honey being one as example, soothing to some, throat razors too me. Milk and honey, while its an excellent flavor, you might be reacting to it and might have to lower it.
Hazelnut could be a other, but at .5% i highly doubt that, unless you have like me a nut allergy and FW actually using nuts or whatever that could trigger it. But then again, mostly not indicated by throat hit.
Plenty of other factors still could play a role here, as others said, test your bases by itself, every single flavor and then mix this recipe in steps, to see which flavor might not react well with the others, if all the other methods showed no result.
Storage and steep is important as well, especially if you tried “heating” a mix or some other methods people try very often, result could be harshness. Take a look at how you mix.