I've had pull outs with Duke DP's, on a limited basis- I always try to look for correlations and try to understand the "why" when I have misses or situations like this. I believe the two largest contributors to DP pull-outs are:
1) Leverage for the coon- Sapling, tree, brush, etc. leverage points where the coon can grab and pull.
2) Wet Fur: Think about lubricating a ring on your finger when it's stuck, lubricity aids in the coefficient of friction allowing movement.
If I'm trapping lowland conditions or rain/snow with DP's I stake with Berkshires and/or Duckbill stakes- this will eliminate it.
Yes- there can be other contributors but these are the two I have found in pull-out conditions and you had both.