+1
Exact same problem. I can do them consistent if I come back out to switch because it doesn't involve turning my upper body as much, just twisting my hips and legs.
But going the full 180 to regs on tall ledges I have identical issue as you describe. Annoying because once you're in it should just be like a noseslide which is my bread n butter. Literally find switch back tails easier lol.
I feel like its about doing a proper, high leveled ollie while opening your shoulders fully, then only put your tail/nose in once your body is basically already in a regular backside noseslide position and the board is high enough from the ollie. Idk tho, never really put in the effort to try.