Check the mfgr's warranty. You may be covered under the "lemon law", as long as your previous calls and present diagnosis are properly documented.

Try forcing a defrost by turning it off at the control inside the frige section, then back on, three times within 6 seconds. If it goes into defrost mode, the ADB is good. if not, then you need to replace the board. These boards are very sensitive and need to be surge protected. You can either get an individual surge protector (appliance rated), or check with your electrician for the cost of whole house protection. Where I live, the cost to protect an average (1800-2200 sq. ft.) is between $200 qbd $300.