Sea pickles are supposed to work just like turtle eggs, right? You put one, and then place another one, and the latter will form next to the former one, while the former one stays still. But the case for sea pickles is that the pre-planted ones' locations keep changing when another one is put within the same block. It doesn't seem to be working as intended.
The second screenshot below shows what happened when I put another pickle within the block the cross mark points at in the first screenshot.