What effect would poor circulation of the melting point bath liquid have on the observed melting point?

I believe that poor circulation could either cause the melting point of the compound to be higher or lower. Melting point is the temperature at which the solid and liquid forms of a pure substance can exist in equilibrium. As heat is applied to a solid, its temperature will increase until the melting point is reached.

Exothermic,  physical change after it is already baked