I had the same problem.
System: intel i7 4770K (4th gen), nvidia 980 ti, latest drivers (actually a pretty fresh Win10 install, 3 weeks young and clean), Shotcut hardware encoders not activated,16GB RAM, some vids on SSD, some on regular HDD (doesn’t matter to the crash party).
Sources: Mostly AVC 1080p, some with variable, some with fixed framerate - the speed change death is an equal opportunity disappearing act.
Fiddling with clip speed using OpenGL: Adios muchachooos!!
Software (Mesa): “Adios muchachos” encore.
Automatic: Vamanos, mas adios muchachos! (I guess it chooses “OpenGL” or “Software”…)
DirectX (ANGLE): WORKS! Yeeeehaw!
Nice to know: Using OpenGL it actually works if converting the clip to “edit-friendly” first.