d) Justified response to a reweighting of the case in the board's preliminary opinion 

In T 1780/19 the respondent (patent proprietor) submitted test report P6' after receiving the summons. The board viewed the repeated test reported there as supplementing the test carried out by the appellant (opponent) and described in E21. E21 had already been discussed in the opposition proceedings, but another finding had then been added on appeal. In its preliminary opinion, the board attached particular importance to this addition, which resulted in a reweighting of the matters at issue in the case. The board found that the filing of the repeated test in P6' was to be seen as a response to this. Moreover, consideration of P6' did not disadvantage the appellant, who had opened the way for this amendment by submitting an incomplete test report.

See also T 935/19 (new submissions relating to Art. 83 EPC in response to a point made clear in the board's preliminary opinion).