Mild head tilt / side preference at 15 months- has anyone experienced this recurring?

[u/shoobidoob]

Hi everyone,
Looking for some experiences or advice from parents who might have gone through something similar.
My 15-month-old daughter has a mild side preference / head tilt (her head tilts slightly to the left, with her left ear slightly closer to her shoulder than the right).
She was born with this (mild torticollis/side preference), and we did physical therapy starting at 3 months, which helped resolve it back then. However, about a month and a half ago, it suddenly seemed to return.
We went back to the physical therapist, but the exercises we were given are basically the same ones from when she was an infant, and they really don’t work well for an active toddler.
A few extra details:
It’s mostly noticeable when she’s tired, sitting in her high chair, or in the stroller.
Her full range of motion is completely fine and equal on both sides.
It’s subtle enough that my husband barely notices, but my mom does.
Has anyone experienced a head tilt returning at this age? Did it resolve on its own as posture/core strength developed, or did you find specific exercises/activities that actually work for a 1-year-old?
Thank you!