I use OpenMPT 1.18.02.00 (development build)
Well, that has already been superseded by OpenMPT 1.18.03.00 in August, which fixed a few crashes here and there, not related to c&p I think, but your problem might just as well be related to something completely different and it was just bad luck that it happened while pasting.
I've desactivated it because I often work on big songs that takes several seconds to save (40Mb, 200 samples...).
It might be worth buying a small SSD for current projects in that case.
I don't have one but I have autosave set to save every minute. I don't really notice that even with my bigger tracks (10-30mb), as Windows' cache is doing a rather good job in this case.