Fridge is warm but Freezer sometimes warms up

Hi, I have an Amana Refrigerator ABB2224WEB2 Fridge The fridge got warm for a few days but the freezer continued to work. Then after a couple of days the freezer went into a thaw. After the thaw, everything started working again. Everything worked for about 5 days then the fridge went warm again. I replaced the main board but it still didn’t work. Again, the freezer followed suit. We emptied everything. The freezer didn’t do a complete thaw like the last time. When we looked in the back, I could see frost on the back wall. In the fridge you could feel a lite coolness coming from the damper. We did some self-tests and the damper worked and we could hear the fans running. I unplugged the fridge and let it thaw overnight and when I plugged it in this morning everything seems to be working. I’m guessing I have a defrost issue of some sort but I’m stuck on what I need to fix it. Can you assist?