I used to get them pretty often, but haven’t done one in a few years, so take it with a grain of salt.
I used go stay stuck and get bucked backwards just like you, what really helped me was once I was in position, i’d put most of my weight on the toe side wheel and it’d just powerslide right through. Much easier said than done of course, but once I figured this out they became easier. I’d always stick if my weight was distributed evenly. Also, don’t pop too high, you want to get just enough pop so your wheels end up in position, which wakes it much easier to slide. If you land too hard it’ll stick no matter the ledge.
Now i’m old and don’t skate much anymore and it’d probably take a whole day to get just one.
If you live somewhere where it’s cold, find a patch of ice or smooth marble and practice back noseblunt powerslides, that’s how I figured out the weight thing