Preserving unique content in instances when updates have been applied to component masters

[tank666]

What changes have been made to the main component in the library? Did you delete the text layer and add a new one? If so then :

@tank666

Each layer has its own unique ID. By deleting a layer and adding a new one, the layer IDs will no longer match between the library objects and the design file objects, which is why the overrides are reset.