In T 1309/16 the board admitted new citations (D23-D25) forming common general knowledge that had been filed in response to a new line of argument in its preliminary opinion.
In T 1038/18 the appellant (opponent), in reply to the preliminary opinion expressed by the board in its communication under Art. 15(1) RPBA 2020, submitted for the first time during the appeal proceedings arguments of lack of inventive step over document D1 in respect of a claimed feature that did not correspond to the features identified by the opposition division as new but had subsequently been identified in the board's preliminary opinion as the sole distinguishing feature over document D1. The board did not agree with the respondent (patent proprietor), who objected that the appellant's arguments could have been submitted with the statement of grounds of appeal as precautionary measure and therefore should not be admitted. It instead acknowledged cogent reasons justifying exceptional circumstances and, in the exercise of its discretion under Art. 13(2) RPBA 2020, admitted the appellant's arguments into the proceedings.