Unterminated slurs multiply with every save
When a slur occurs that has no type="stop" entry in the mscx file, it not only does not display, but multiplies geometrically until the score file spans megabytes and is no longer usable.
See:https://musescore.org/en/node/138061 for details and sample files.
A possibly related issue may be similar treatment of hairpins, see: https://musescore.org/en/node/138691#comment-588421
The common denominator appears to be XML import, so that's probably the place to put some sanity checks in MS.