Something in the mod pack since 1.9 is also causing my machine to lock up totally on leaving a game and a hard reboot is needed this only came about since 1.9 not sure if it is Aslains or WOT but I will remove the modpack and play vanilla to test it.
Since update 1.9 getting a stuttering at the top of my screen testing it with and without Aslains and it is from the modpack have not narrowed down which mod is causing it yet though just thought I'd give a heads up.