Applying double-note tremolo to dotted notes fails, seems to alter meter

I am trying to replicate the IMSLP score for Schubert's D.960 as a learning exercise in MuseScore. The work is in 4/4. In m. 19, there is a double-note tremolo written in dotted half notes, followed by a single beat's worth of sixteenth notes. Per the MuseScore handbook, the user is to enter two notes with half the value of the tremolo total, then apply a tremolo from the palette. However, when a two-note tremolo is dragged on top of two dotted quarters, the notes convert not to dotted-half noteheads, but to *undotted* halves.

Both staves in the measure with the tremolo then also appear to "regress" to 3/4 time, with *both* left and right hand staves accepting only 3 quarter notes' worth of material in the measure in which the tremolo was applied. If the tremolo is undone, and/or if the notes are deleted, this invisible meter change persists in all staves. No meter change is visibly indicated in the score and all subsequent measures continue to accept the correct amount of "metric space" (i.e., we're magically back in 4/4 again as far as MuseScore is concerned).

Picture of source score to be replicated and resulting MuseScore file attached (see m. 19 in the file).

Error encountered using 0.9.6.2 on OSX 10.5.8. Will try to replicate on 0.9.6.2 / Win7.