i have some issues with my GE(GSL25JFTABS) side by side fridge. The fridge was not cooling enough and i noticed the temperature in freezer and fridge going up after 3 days. i saw frost in the evaporator coil and saw the thermostat wires were slightly out of position. replaced that with new GE genuine part. After manually defrosting and changing thermostat, freezer started working fine , but after 3 days same issues started popping out. Saw frost in freezer and temperature was going up so as fridge. Checked the defrost heater in freezer and saw it very black and didn't pass continuity test. replaced it with GE original part.

The freezer and fridge is working fine for 2-3 days. but i saw big temperature variation in freezer. I have portable thermostat in both compartments. Fridge is showing steady temperature under 40F (high is 43F and lowest was 32F), but freezer thermostat is showing high as 45F and low as -10F) . i haven’t put anything in freezer yet to test it out. This Cycle in freezer happens every day, each night i reset the thermostat and next day morning freezer shows high of 45F to -10. the ice is not melting in freezer… Some of the food looses frozen feeling for some time and then again freezes when temp drops.
any idea why this is big temperature variation is happening in freezer?

any help is appreciated.