Playback oddity with ties

Please look at the attached file and listen to playback. I hear the piano play tied notes as if they were slurred, i.e. the second note played again. For example bar 13 - 15 the ties across the barlines sound as two 1/4 notes rather than syncopated half notes as they should.
It is possible that the error here is mine. I am just baffled and would like to know if this may be a bug or what else is going on.
Thanks, everybody!
The score is a work in progress; any typos will be corrected in the proof reading phase (if I find them anyway). If you are curious it is the fourth movement of a sonata for cello and piano by the German composer Emilie Mayer, typeset from the autograph.