X-DNA bug

[Reidar]

I have 3 first cousins, they are all full brothers. They have all strong match on the X-DNA, but no full matches (195.95 cM). But all of them get full matches on the X-DNA with a woman who is totally unknown to all of us. This looks totally absurd to me, it looks as a serious bug. From what we know about the X-DNA, this seems as an impossible result. Has anyone experienced bugs of this kind??

[John McCoy]

There have been several similar reports here recently. I believe at least a few of them were reported to FTDNA customer service and found to be false matches, due to some sort of technical issue (the nature of which I don't think has been explained). If the unknown match does NOT share significant autosomal DNA, yes, it is extremely unlikely that the full X match is real.

[georgian1950]

You could construct a synthetic kit for a female which would have an X-match with every male kit. GEDmatch probably needs better filters on what it allows.