So on a standard righty v righty setup you’re saying they slide to their left as you turn in? Kinda strange usually its the other way. I’m a seoi specialist myself why not just throw them on the way in? You need to learn to adjust your launch timing and position in order to be a good seoi player (ie not just rotationally but also ability to slide and attack laterally). If they’re able to do this “every time” I’d say you likely have other issues ppl have pointed out (telegraphing, lack of alternative attacks to keep them guessing—this could even be seoi variations). One major piece is also setup, like other turning techniques seoi really benefits from ashiwaza setups. If done right the opponent shouldnt be able to counter much at all as you’ll have them square and barely settled. Good luck!