According to the established case law of the boards of appeal, the violation of the principle of the right to be heard is considered as a fundamental deficiency of first instance proceedings and remittal is often ordered accordingly, as e.g. in T 125/91 (no opportunity to comment), T 808/94 and T 892/92, OJ 1994, 664 (no oral proceedings arranged), T 1399/04 (no opportunity to comment), T 1077/06 (no opportunity to comment), T 1536/08 (evidence not considered), T 477/13 (refusal of request for postponement of oral proceedings). For further details, see chapter III.B. "Right to be heard".
In T 1505/06 the board was unable to review the decision of the opposition division not to postpone the oral proceedings and was unable to ascertain whether the right of the patent proprietor (appellant) to be heard had been respected. It therefore had no choice but to remit the case to the opposition division for further prosecution.