According to Art. 24(3) EPC an objection on the ground of suspected partiality is not admissible if, while being aware of a reason for objection, the party has taken a procedural step. Nor may it be based on the nationality of members. Additionally, the boards have rejected objections as inadmissible because they were not reasoned or were a mere repetition of a previously rejected objection.
Source: http://www.epo.org/law-practice/legal-texts/html/caselaw/2019/e/clr_iii_j_3.htm
Date retrieved: 17 May 2021