Is it normal that slow songs trip me up vocally?

I don't expect too many responses, if any at all, because I haven't noticed many singers around IIN, but I've been curious anyway, so I'm asking.

I'm a trained singer. Lately, my instructor has noticed I've been having trouble with slow songs. She's always observed that I'm quite "robotic" in my pitch attack and timing. She jokes that I have auto-tune built in to my larynx and that my brain is auto-quantized. Now, these "problems" don't matter much in quick songs, in fact, they're essential to sounding smooth and natural. My runs are quite speedy and crisp, and if a song requires very little scooping and a lot of staccato, I'm up for it. But I've always noticed I sound very stilted, strained, and unnatural on a slow ballad, and so, now, has my teacher.

My teacher has told me that there is a place for imprecision in music, and that hesitation can be used very artfully. My instructor has warned me that I'm never going to carve a unique niche with my voice, unless I find my "place". I can sing triplet, duplet, swung, and blue notes; that's not the issue. The problem is I can't seem to easily vary my intonation and attack according to the emotion of the song. I guess I must be subconsciously focused on perfection. Even my vibrato sounds too "perfect". Even before I was trained, I sang like this.

Another problem I have is that I can never decide when to end long held notes. I can hold a note steadily for a VERY long time, but for some reason, it never feels natural just "letting go" and easing into vibrato when I begin to run out of breath. I want to end the note on the bar.

I'm frustrated, because I really want to sing more naturally. I need to get into a new head space.

Have any of you other vocalists had this problem and overcome it? Is my teacher wrong for thinking of this as a major problem?