That doesn't happen to me, maybe do some troubleshooting?getting 1.6.4 packs loaded on curse/twitch was a chore in itself since it fubars the sounds. had to load up a new instance in mmc and copy the directory over but that works great.
I'm also playing 1.6.4 packs again. Currently another hardcore BnB run, then Crash Landing. So hard to let go of them.