Take what I've got to say with a grain of salt since I'm not close to your deadlift numbers and would probably be able to learn more from you than teach you.
You might just be over analyzing and just need to put in the time and practice with that new movement. What you mentioned also sounds like a distinct possibility. I know that can happen with my warmups.
Something else to consider is that maybe your not pushing out from the sides of your feet enough. Spread the floor is the cue for this one when it comes to wide stance anything.
I used to have the problem you explained with box squats. It was because I was only pushing into my heels. Once I start pushing from the entire outer side of each foot did I put that problem to rest.
I like EMOM singles with 80-85% for deadlifts for drilling in form and any new cues. But I'm sure you have an idea of what works well for you at this point in that regard.