OP-1 Sample pitch shift problem

I’m a fairly new OP_1 user , maybe someone out there can suggest a solution to a problem I have encountered?
have added some samples to my OP-1 and very carefully mad sure they are
at middle C but when the OP-1 takes them and converts them to a patch
the note shifts. The first one (a Hang Drum) shifted up to an A, I
corrected this by shifting the sample down by the same amount. So I then
tried a 12 string guitar sample using the same method but it turned
into a G# and took quite a bit of trial and error before I managed to
get it about right.

My question is this. How can I get the sample
to the correct pitch for the OP-1 to convert or how can I edit the OP-1
patch to correct it?

Any suggestions gratefully received.

discussed at length here http://operator-1.com/index.php?p=/discussion/comment/8080/