Crash on slurs

I have a score created in 2.1 originally that is consistently crashing the latest MuseScore 3.0 master build.
Works OK in 2.1.
Can't quite trace what is causing it, but I'm guessing an object is being deleted too soon.
Stack listing below:

Getting a SIGSEGV when calling toSystem in Spanner.cpp
1 Ms::ScoreElement::isSystem scoreElement.h 237 0xdcea4d
2 Ms::toSystem scoreElement.h 384 0x83c5c4
3 Ms::SpannerSegment::system spanner.cpp 50 0x83c73b
4 Ms::SpannerSegment::setSystem spanner.cpp 59 0x83c752
5 Ms::SlurTie::fixupSegments slurtie.cpp 540 0x83b1c1
6 Ms::Tie::layoutFor tie.cpp 676 0x83859c
7 Ms::Score::collectSystem layout.cpp 3115 0x7c6018
8 Ms::LayoutContext::collectPage layout.cpp 3364 0x7c7e26
9 Ms::LayoutContext::layout layout.cpp 3653 0x7c9830
10 Ms::Score::doLayoutRange layout.cpp 3640 0x7c972e
11 Ms::Score::update cmd.cpp 222 0x8a4ce5
12 Ms::Seq::seek seq.cpp 1110 0x4f1fef
13 Ms::Seq::start seq.cpp 326 0x4ef0bb
14 Ms::ScoreView::changeState events.cpp 812 0x41d387
15 Ms::ScoreView::cmd scoreview.cpp 1742 0x40bb67
16 Ms::ScoreView::cmd scoreview.cpp 1678 0x40b72f
17 Ms::MuseScore::cmd musescore.cpp 5132 0x49fa9f
18 Ms::MuseScore::cmd musescore.cpp 4672 0x49d638
19 Ms::MuseScore::qt_static_metacall moc_musescore.cpp 740 0x6c77e3
20 ZN11QMetaObject8activateEP7QObjectiiPPv 0x68c03046
...