When your soap seizes is when the soap mixture suddenly becomes very thick/hard and you get soap on a stick. Usually this takes place when the fo is added. Some fos are notorious seizers - like florals for example. To help avoid seizure, soap with your oils and lye cool, hand stir and add your fo to your oils. Also soap with full water. These steps might help, but sometimes you get that oil that will seize no matter what you do.
Warming up your FO's will help with this too, if you soap warm. You can add your FO to a little of your oils and mix it in at trace too. This will help not having "soap on a stick" situation.
I stick blend until emulsification (light trace) then whisk in my scents by hand.
Yep, PhillipJ — take a look at my Botched Batch thread, if you haven't. You'll see what can happen when you add a FO (unwarmed, unmixed with fixed oils) to a batch of too-warm soap batter.
There's also the idea that the high percentage of Mango butter I used, along with Olive Pomace (a supposed trace accelerator), set the stage for the mess you see in the pic. An experienced soaper left a comment in my blog (you won't see it, cuz I haven't transferred all the comments from my old blog).
But I do know that I could feel the warmth of the batter, when I was hand stirring and something went off in my head, "This batter seems awfully warm". I wasn't totally sure about what was going to happen, after I added the FO. But the result was clear, in seconds. You can laugh. I did...about 15 minutes after.