New Y-Tree change from hg R1a1a to hg BT. Whut tha ...?

[Geolocke]

I am co-admin of the Locke Surname project and like many I have been trying to come to grips with FTDNA's new Y-Tree and all it's changes, but we have one member whose hg changed from R1a1a to hg BT (SRY10831)

I know that this is probably just another SNP mix up, but this one really has me scratching my head. FTDNA has this group listed as follows:
BT --- SRY10831 M139 M299 M42 M94 PAGES00024 PAGES00026 PAGES00081 --- (BT-SRY10831)

That's it. that's the whole hg.

I found the following description on snpedia http://www.snpedia.com/index.php/Haplogroup_BT_%28Y-DNA%29

"Haplogroup BT (Y-DNA) descends from Haplogroup Y (Y-DNA) and split off from Haplogroup A (Y-DNA) in North East Africa approximately 55,000 years ago. It is the parent Haplogroup of all modern Y-DNA Haplogroups except for A. It has two haplogroups descended from it:
Haplogroup B (Y-DNA)
Haplogroup CF (Y-DNA)
Previously known as Haplogroup BR (Y-DNA) and Haplogroup YxA (Y-DNA)."

This seems like a fairly big jump in hg's even to my untrained eye. I'm sure that it is just another kit whose hg will be in need of clean-up after the dust settles, but I'm wondering if anyone else has see such a drastic shift in hg designations.

[lgmayka]

Yes, this is common. The root problem is this:

If an FTDNA customer has a test result for a multiply occurring SNP, such as SRY10831 (which appears twice in the haplotree), and no other disambiguating SNP test results, FTDNA's algorithm simply picks one of the occurrences as correct. What the algorithm ought to do instead, is to check nearby haplotypes for disambiguation.

Because of this bug:

R1a men are getting assigned BT, due to SRY10831
I2a men are getting assigned G, due to P37
I2a men are getting assigned J, due to L147
etc.

[Geolocke]

Yeah, that's what I just figured out. There are two (2) variants of SRY10831. SRY10831.1 = hg BT & SYR10831.2 = hg R1a1. FTDNA is only listing this SNP as SYR10831, so they probably had a computer algorithm Look for the New SNPs and 10831.1 (hg BT) came up first. But in reality, this kit is probably still R1a1. I will contact FT-DNA and ask them to look into it. This same situation may explain other folks having changes from one hg to another. (variants being counted as a single SNP and not picked up by the computer's algorithm)