The problem is that the per-data-item loop may fail to parse a data item in iterations after the first iteration, because the len parameter used when invoking sldns_str2wire_rr_buf() with dual meaning ('available' on input, 'consumed' on output), is not readjusted from one loop iteration to another.

The result is that the tag data item parsing fails, unless the amount of buffer consumed in previous iteration is larger than the amount required in the current iteration.