Maytag Plus Side/Side slow loss of cooling to the...

Question

This is a 7 year old Maytag Plus Side by Side. The air vent from the Freezer to the Fridge getting blocked with ice over a period of time. Shutting down the complete unit and waiting for the ice to melt is one unacceptable way of solving the issue (until next time) The freezer side shows no sign of problems. I guess the question is what could be causing the ice buildup, I suspect it could be in the electronic controls