That's the first post in this blog, and it's just not to forget send ODA feedback that their DWG specification has mistake in it:

Page 82 (AcDb:Classes)

The ending sentinel should be like this:

\x72\x5E\x3B\x47\x3B\x56\x07\x3A\x3F\x23\x0B\xA0\x18\x30\x49\x75

second byte is 5E instead of 5L in specification. This mistake has place in R13-15, and occasionally in later pages.