rtorrent sometimes works better than transmission, but on big files (>500mb) it also happens, though somewhat less often. Going to default values in Swappolube seems to help a bit, but it is still hit-or-miss situation. Another approach is having htop (as root) open in an xterm window and killing transmission as soon as it starts to misbehave, on subsequent starts it will sometimes run well. This is probably a statistical result as it sometimes will just work