It seem that having your skeletal mesh window open and reimporting the entire FBX file will crash rocket just after the chuck processing, this was in the beta 4/newest build
EDIT : by reimport i meant, importing the same FBX as a new asset and just saying yes to all to overwrite.
Fatal error!
Address = 0x2fec93c0 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\fbxsdk-2013.3.dll]
Address = 0x2fec391d (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\fbxsdk-2013.3.dll]
Address = 0x30066e47 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\fbxsdk-2013.3.dll]
Address = 0x3134fb06 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-UnrealEd.dll]
Address = 0x313562e6 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-UnrealEd.dll]
Address = 0x312e1d12 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-UnrealEd.dll]
Address = 0x312f6d0a (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-UnrealEd.dll]
Address = 0x2a284484 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-AssetTools.dll]
Address = 0x2a283054 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-AssetTools.dll]
Address = 0x28f55208 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-ContentBrowser.dll]
Address = 0x28f4f1ef (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-ContentBrowser.dll]
Address = 0x28f5510a (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-ContentBrowser.dll]
Address = 0x31f605ff (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-Slate.dll]
Address = 0x31f63ee8 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-Slate.dll]
Address = 0x31f480bc (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-Slate.dll]
Address = 0x31d2c2aa (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-Slate.dll]
Address = 0x31d4f36e (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-Slate.dll]
Address = 0x31dc1f86 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-Slate.dll]
Address = 0x31dba6b1 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-Slate.dll]
Address = 0x34478bfc (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-Core.dll]
Address = 0x3446acca (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-Core.dll]
Address = 0x34479556 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-Core.dll]
Address = 0x344668d2 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-Core.dll]
Address = 0x6b92171e (filename not found) [in C:\WINDOWS\system32\USER32.dll]
Address = 0x6b9214d7 (filename not found) [in C:\WINDOWS\system32\USER32.dll]
Address = 0x3449e559 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-Core.dll]
Address = 0x34479beb (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor-Core.dll]
Address = 0xa95a5e64 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor.exe]
Address = 0xa959cb8c (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor.exe]
Address = 0xa959cbfa (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor.exe]
Address = 0xa95a772b (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor.exe]
Address = 0xa95a83c3 (filename not found) [in F:\Program Files\Rocket\1808360\Engine\Binaries\Win64\RocketEditor.exe]
Address = 0x6b2e1832 (filename not found) [in C:\WINDOWS\system32\KERNEL32.DLL]
Address = 0x6bd5d609 (filename not found) [in C:\WINDOWS\SYSTEM32\ntdll.dll]
Address = 0x6bd5d609 (filename not found) [in C:\WINDOWS\SYSTEM32\ntdll.dll]