Ugh is right!! Could be stem blight but doesn't really look like that. Did you fertilize heavily? Is the ground moist, dry, or wet?

We have a lowbush blueberry shrub that was peed on by one of the neighborhood dogs. It is planted near the sidewalk. Part of it turned brown, and looks a lot like your shrub, with nice green leaves still growing in other places.

My dog pees on stuff all the time, that would be multiple times for that bad of damage. Otherwise though I have no idea? That is pretty bad damage. If the ground cover showed symptoms that would tell us it was urine, or herbicide, but the cover looks good. Dogs miss a lot, it would also be brown. Are you watering enough? it looks dry to around plant. Give it more room, and cut that ground cover back. Add more mulch. That plant may not make it.

Could also be root damage from grubs or other burrowing trouble makers.