I have experimented with SloMo using my GoPro 1080 50p clips. My output is 25p. To get real quality SloMo you need 1000 Fps or more. Most of us don't have access to a high speed camera so we use what we have.
In PDR13 I have found Video Speed is OK at .5 but poor results at slower speeds. I get acceptable results down to .2 using the Interpolation option - and have experienced no crashes with either.
Power Director 13&14 Ultimate, Photo Director 6, Audio Dir, Pwr2Go 10
Win 10 64, Intel MB DH87MC, Intel i5-4670 CPU @ 3.40GHz, 16Gb DDR3 1600, 128Gb SSD, 2x1Tb WDBlue 7200rpmSATA6, Intel 4600 GPU, Gigabyte G1 GTX960 4GB, LG BluRay Writer