According to the established jurisprudence of the boards of appeal, a misinterpretation of a document normally constitutes an error of judgment rather than an error of law and is therefore no "procedural" violation, let alone a substantial one (T 1031/12). In T 162/82, OJ 1987, 533, the board held that an error in interpreting a document could not possibly be regarded as a procedural violation (see also T 1049/92, T 976/11).
In T 367/91 the board stated that to base a decision only on a wrong assessment of prior art and/or the claimed invention had to be regarded as a substantive error, not a procedural violation (see also T 144/94, T 12/03, T 1340/10, T 997/15). In T 68/08 the board held a wrong assessment of the claimed invention (or of the prior art) would always be a substantive issue.
In T 17/97 the appellant's request for reimbursement of the appeal fee was based on the fact that the opposition division had disregarded a document. In the board's judgment an erroneous assessment of the relevance of a document did not, by its very nature, constitute a procedural violation within the meaning of R. 67 EPC 1973.
The misinterpretation of a document does not constitute a procedural violation (T 1049/92; T 162/82, OJ 1987, 533; T 1031/12). In T 588/92 the board pointed out that a different opinion on the specialist knowledge to be applied when interpreting the technical content did not amount to a procedural violation.
In T 860/93 (OJ 1995, 47) the board found that that even though there had been a gross error of judgement on the part of the examining division there was no procedural non-compliance of the kind which was a condition precedent to R. 67 EPC 1973 taking effect.
In T 863/93 the board held that it was the established jurisprudence of the Boards of Appeal that in order to fall within R. 67 EPC 1973 a procedural violation as opposed to an error of judgment must have occurred. It concluded that the issue raised by the appellant, i.e. the examining division's misunderstanding of D1, was a matter of judgment which did not justify the reimbursement of the appeal fee.
In T 970/10 the board held that an incorrect assessment of a document with regard to its date of availability to the public related to a factual error in respect of the substantive requirements under Art. 54(2) EPC, and not to an error in respect of procedural law.
In T 976/11 the board disagreed that the change of the closest prior art alone could constitute a substantial procedural violation. It held that an examining division had the procedural discretion to revise its objection of inventive step, including the choice of the closest prior art, at any stage of the examination proceedings, including the oral proceedings.
In T 658/12 the board held that an insufficiently reasoned decision had to be distinguished from a decision that had faulty or unpersuasive reasoning. The board concluded that while the COMVIK-approach may have been incorrectly applied in the case in hand, this was a substantive issue, only involving judgement. Thus, the board found that the decision was reasoned in the sense of R. 111(2) EPC. The board also found that the examining division had not acted unreasonably, as claimed by the appellant (applicant), by not admitting the second auxiliary request. The board held, therefore, that there was no basis for reimbursement of the appeal fee (see also T 690/06).
In T 680/89 the board found that it did not amount to a procedural violation if the examining division wrongly finds that a claim is not sufficiently clear to comply with the requirements of Art. 84 EPC 1973, even where there has been a possible error of judgment and failure to seek clarification from the appellant. It concluded there was no basis for ordering reimbursement of the appeal fee in accordance with R. 67 EPC 1973.