I had a similar issue a while ago. Try increasing your destructible attack range to at least 12-15, the center of the object might be too far. Also, I leave "ignore non-blocking obstacles" checked off, I find that helped some of my stucks.
Try turning off destructible. Also there have been people reporting lower GPH but reinstalling DB fixed that for them, maybe it'll work similarly here.
If you people getting stuck are using Giles Trinity 1.5 or higher, the Giles Unstucker is now OFF by default, if you enable it, it should resolve all issues.