Defrost does not stop

Question

I have a GE side by side Mod# TFX25JRBAWW.My problem is sometimes when it defrosts it stays on defrost until I play with the temp. control. Sometimes that doesnt work and I will unplug it for 5 or 10 min. and it will start to cool again when I plug it back in.Someone suggested replacing the defrost timer and another person suggested replacing the temp. control. I was thinking about replacing both. Any suggestions?