FTDNA mystery

[aghadowey]

A few years ago OH did DNA test. The 3rd highest match (in 2019) was R F*son- they shared 105 cM. I put the match into DNA painter and sent an email off. This week I finally got a reply (my original email overlooked in a folder) and was hoping we could find a connection. Back in 2019 I had established is was a paternal match to OH.
Simple, right? NO
Revisiting FTDNA, and the notes I initially made, the match was 105 cM. When I look now FTDNA shows the match is only 86 cM (longest segment 49 cM). Checking back in DNA painter I see only 2 segments matching (47.5 and 7.1)
So, why the difference between 105 and 86 centimorgans?

OH also has a match with E F*son (in 2019 was 60 cM but is now 16 cM).

Another kit I manage also matches R F*son as well as a D M F*son and a D F*son but those results look unchanged.

Any ideas what has happened?

[AnotherDay]

For a long time, FTDNA counted every speck of DNA - which meant the shared cM amounts were inflated. A year or so ago, and after much criticism, FTDNA stopped including tiny specks in the shared cM amount. So the 'missing' DNA would be those tiny specks. And the revised shared cM amount will better reflect the likely relationship.

[aghadowey]

Thank you for such a quick and easy to understand response.

I can understand they decided to make changes in amount of centimorgans (can't remember seeing this announced but perhaps I missed something) but the earlier results have also changed on DNA Painter.

In another example (and if I go through everything there will be similar, I'm sure) is a match with 4th cousin once removed. Previously was 54cM now down to 23cM saying longest block is 17cM but all that shows is 13.3cM on 1 chromosome. Surely if the longest block is 17 then it should show more than 13.3?

[AnotherDay]

There might be some number rounding going on.

I share 23 cM with Ted. The summary says our longest block is 17 cM. When I look at the Chromosome Browser, I match Ted on 2 Chromosomes, with 6.6 cM on one and with 16.6 cM on the other.

I share 23 cM with Maureen, apparently with a longest block of 16 cM. The Chromosome Browser show a 6.9 cM segment and a 16 cM segment.

I share 23 cM with Michael - longest segment 23 cM. And that is what the CB shows.

[aghadowey]

Thanks again for your reply. Your examples of rounding numbers doesn't seem the two figures are too far off, whereas mine ...

Don't have the original figure to hand but there's also a match to a sister of 4th cousin once removed that I mentioned. Current figure is 46cM (longest black- 25 cM- rounded down to 24.68 in CB which is much like the results you have).