If you're steady then you're steady, it shouldn't matter what yardage it is. It's odd that you'd be steady at 40 yrds and not steady at 55 yrds.
This almost sounds like when you use a low power scope vs a higher power scope. With a low power scope you appear to be holding on the target with out wobble but with a higher power you magnify your shake so you see it more and it appears that you're wobbling when actually you're not, you just see it more thru the higher power scope.
Using that analogy and applying it to archery, maybe at the longer range you just "see" your wobble more because the target looks smaller.
If this was just a hunting situation I'd simply tell ya' to not shoot beyond 40 yrds but since it's target shooting you need to get a handle on it somehow. Maybe a coach can help you figure out what's taking place at longer yardage.