Samsung RS261MDRS ice buildup

Samsung side by side RS261MDRS (this is one where fridge and freezer are independent of each other). No problem on freezer side but Refrigerator side coils build up with ice. The manual forced defrost (secret menu) works fine and the heater heats up like it should. The defrost sensor measured way out of the expected range (ohm meter) replaced the defrost temp sensor with genuine Samsung part and that made no difference.

Everything else works great and freezer side doesn’t have the same problem.

Running the forced defrost causes the element to heat up correctly and the sensor has been replaced, does that leave only the control board left to suspect? Is there a specific connector I can check or test measurement I can make to confirm the defrost board is bad before I order a new one? Or should I just do a forced defrost every month?

how often should the defrost be automatically cycling if the defrost timer were working properly?

thanks in advance!