Water overflowing of defrost water pan. The amount of water flowing into the back defrost water

Question

The amount of water flowing into the back defrost water pan overflowed; it has never done this before. The freezer seems to be operating normally, though the refrigerator lately has seemed to be colder than it used to be at the same setting. The owner's manual, unfortuanately, has nothing about this in "troubleshooting".