In-Slab Duct Damage

We noticed that our laundry room and downstairs powder room were cold this winter, and when the heat was on, minimal airflow was coming from the vents. I used my borescope to check out and it looked like there was damage, so we called in our local HVAC company with a better quality camera, and sure enough, right where the bathroom line tees off, it's rusted out completely.

In my crude diagram below, the break is at "3". The area between the heater and the tee (around "1") is the family room, with in-floor vents that work just fine.

Attachment 821370

This is under the slab, and I'm trying to weigh my options:
1. Cut into the slab and repair the tee at '3'.
2. Re-line the duct "non-invasively" (is this even a thing?)

This is the only part of the duct that is damaged, and presumably the only part that would need replacement. Also, in the summer, there is a damper that is closed to minimize the A/C into those areas (they don't get uncomfortable).

Re-routing into the attic isn't an option given the "geography" of where the ducting is located - it would require running up a narrow external wall that has a window taking up approx 90% of the width of the wall.

Thanks in advance.

source https://hvac-talk.com/vbb/showthread.php?2225658-In-Slab-Duct-Damage&goto=newpost