It's not the wick that is buring, it's your e-liquid.
When a coil doesn't get enough e-liquid, the temperature goes up, because there is no e-liquid to convert to vapor, and your e-Liquid burns. It's kinda like when you doa Dry Burn.
You can increase wicking on a Sapphire by removing a very small portion of the wick. You would remove the tube, pull the wick out of the holder, remove a strand, wet the wick in your e-Liquid and then push it back in.
But if you remove too much wick the coil will flood or the carto may leak.
So if youy decide to pull remove some of the wick, only take a very small amount and see how it goes.
Should I maybe try thinning my liquid? I use 100% vg