Ok, I think I understand why the installer does not complains: the detection of DVD-Form was fixed in 188.8.131.52, hence after the previous web update (184.108.40.206).
Yes, 220.127.116.11 had the bug of not recognizing correctly DVD-RAM only devices, and this is fixed in 18.104.22.168 as you noticed.
What surprizes me is that your media are mounted by 4.2 as you say that the filesystem INCDFS is shown (I assume you check the volume properties), but however are 'unreadable'. Can you detail the unreadable? Cannot see files? Cannot read them? Cannot write/modify/delete files? Wrong volume label? More problems?
Also, I suggest to run Philips UDF Verifier on the discs causing trouble ( http://www.extra.research.philips.com/udf/
). This tool will tell us if the UDF filesystem on the discs is valid or not.