I admit to finding this thread a bit confusing!! Without trying to second guess the root cause of the OPs experience my first observation is the pretty awful state of the bearing cups on both headests shown in the thread.
Personally I would never buy a carbon framed bike but for those happy to do so it is worth noting that the most susceptable part of the frame is the headest......more especially if, for whatever reason the headset assembly is, or becomes, loose. The stress forces on the headtube area are significant.
I really cannot see how a bike shop or even a reasonably competent home mechanic can mess up a fork change, especially if all the original headset elements are merely re used.
A headset can become loose, especially shortly after assembly, and need re a djusting. This is typically caused by grease getting displaced during use but can also be due to some settlement of bearings themselves......or later on a bit of bearing wear.
I also do not agree with headset cap "torque specs". The idea is to remove all vertical play between bearings and cups without causing any binding of the bearings. How much torque on the top cap that requires depends to some degree whether the top cap bolt is greased or not etc. one thing for sure, is that no adjustment is going to a permant fix if the bearing cups are not a completely level and flat surface for the bearings to work against.
I have also experienced top caps that are so flimsy, they are not reliable in maintaining adjustments made.........and typically 8nm tightening of the stem on the steerer is not going to prevent some movement if the assembly is not snug to start with.
Lastly, paint does not crack. A crack line in paint signifies a crack in the composite it sits on. Composite frames...especially light ones.....are typically constructed using UD carbon layers.............I would expect the area around the bottom of a headtube to be additionally wrapped with a matrix carbon given the varying directions of stress applied there. The Ops photo suggest that is not the case here...............the question is whether the crack has compromised the entire composite or not and that can only be determined by a professional with the right equipment.
Personally I would never buy a carbon framed bike but for those happy to do so it is worth noting that the most susceptable part of the frame is the headest......more especially if, for whatever reason the headset assembly is, or becomes, loose. The stress forces on the headtube area are significant.
I really cannot see how a bike shop or even a reasonably competent home mechanic can mess up a fork change, especially if all the original headset elements are merely re used.
A headset can become loose, especially shortly after assembly, and need re a djusting. This is typically caused by grease getting displaced during use but can also be due to some settlement of bearings themselves......or later on a bit of bearing wear.
I also do not agree with headset cap "torque specs". The idea is to remove all vertical play between bearings and cups without causing any binding of the bearings. How much torque on the top cap that requires depends to some degree whether the top cap bolt is greased or not etc. one thing for sure, is that no adjustment is going to a permant fix if the bearing cups are not a completely level and flat surface for the bearings to work against.
I have also experienced top caps that are so flimsy, they are not reliable in maintaining adjustments made.........and typically 8nm tightening of the stem on the steerer is not going to prevent some movement if the assembly is not snug to start with.
Lastly, paint does not crack. A crack line in paint signifies a crack in the composite it sits on. Composite frames...especially light ones.....are typically constructed using UD carbon layers.............I would expect the area around the bottom of a headtube to be additionally wrapped with a matrix carbon given the varying directions of stress applied there. The Ops photo suggest that is not the case here...............the question is whether the crack has compromised the entire composite or not and that can only be determined by a professional with the right equipment.