Washing machine Spin cycle issue when heavy stuff only

My kenmore 70 series washing machine does agitate and will spin if the load isn’t heavy stuff like towels, or a full large load. If the load is heavy when wet, the washer has a bit of a burn smell, and it doesn’t spin. If I remove about half of the load it will spin, once a bit of the water wrings from that half, I can add the rest of the load back in and it will spin fine. So it’s only an issue when it’s too heavy, but hasn’t done this the last 10 years until now. So is my motor coupling going out? Or is it something else?