For Web Accesibility purposes we have changed the way fields with labels on top are generated. Pior 12.1 a textblock and a filed with labelposition=none was generated. Since K2BTools 12.1, only a field with its description is generated. If the developer had code to hide or change the caption of a textblock related to a field, this problem may arrse as the textblock is no longer in the WebForm. To fix it do this:
textblock visibility: remove the line of invisibility/visibility of the textblock as the attribute or &variable .visibile property will hide both.
textblock.caption : Use attribute or &variable .caption property instead.