Cold spot in my forge ruining my knife temper, help!

I was tempering a knife blade yesterday and there's this one area that stays cool no matter how I position it. My propane forge is running fine, and I cleaned out the burner, but it's not helping. It's causing soft spots in the steel, which is a huge problem for the blade's strength. Have you guys run into this before? I'm wondering if my refractory lining is worn out or something. Any advice on how to fix this would be great, thanks lol