Ghasts and Creepers can detsroy Rails and more in nether

Cannot reproduce.
Neither Ghasts nor Creepers destroy rails in The Nether under "mobGriefing false"

You have to set mobGriefing to 0, not to false:
/gamerule mobGriefing 0

Edit: Setting mobGriefing to 0, false or chocolate will all do the same... The only recognized keyword is "true"

Unable to reproduce either.

Please force a crash by pressing F3 + C for 10 seconds while ingame and attach the crash report here.

Cannot reproduce with ghasts or creepers.