Spurious key signatures appear when layout changes

Windows 7, GIT commit: 689ecfa

1) new score for flute, D major, enough measures to require at least 2 systems
2) note entry, start entering notes

Result: as soon as you enter enough notes to push another measure to the second system, we get an additional key signature on that system. For example, on my system the second system starts with measure 18. After entering a single note, measure 17 gets pushed to the second system. There is now a key signature on both measures 17 & 18. By the time I've entered 5 quarter notes, measure 16 is pushed to the second system, and now I get three key signatures: