2018 Giant Trinity Advanced. Mechanical.

Custom paint job - removed factory paint, now nude carbon with protective UV lacquer.

The bike is new and has been used on indoor (Wahoo Kickr) for most of the time.

However, 2 long rides - one last weekend (17 Feb 2019), has resulted in this peculiar disintegration of the bottom tip of the seat tube. It is the area closest to the wheel. There was no obvious scratching, bumping or other mechanical/physical lesion which occurred on the ride, which could have caused this damage once off.

I am fairly sure, (based on the sudden worsening of this damage after the second long ride) that it is the dust/grit kicked up from the tire that causes this damage. There was a slight separation of the UV lacquer from frame after the first long ride, however, I thought that was the spray artist's fault. Now I know it has something to do with the riding dynamics.

I fear this might be a problem only I have, however, I would appreciate any advice.