Instead of being absolutely straight, the rovings of one spar cap
showed a slightly wave-like pattern. Alarmed by this discovery we
investigated the spar caps of several other DG-300 wings, which were
in for repair in our factory or other approved maintenance shops. We
found a similar, but less severe pattern at some of these wings too.

The most important question right to the beginning:
"Why may DG-300 spars exhibit this wave-like pattern, and is this flaw
also possible at spars of other DG airplanes?"

The answer:
This specific flaw is limited to the DG-300/303 series!
For all DG wings, except for the DG-300 and DG-600, the spar caps are
manufactured in separate a mould, which allows maximum precision for
the roving placement. While the rovings for the DG-600 are placed
directly into the wing mould, they are inserted into a prefabricated
channel which becomes an integral part of the wing structure. This
allows the same precision for the roving placement. Only the
DG-300/303 uses a different manufacturing method (which is also used
by other manufacturers), therefore only the DG-300/303 is prone to the
described manufacturing flaw.


Notice the statement (which is also used by other manufacturers)