I often get crashes in 4.9 on shader compiling. Sometimes I get following message:
Mismatched shader version for format GLSL_150_ES2_NOUB; did you forget to build ShaderCompilerWorker?
Assertion failed: ShaderCompileWorkerInputVersion == InputVersion
Do you receive the crashdumps on sending or should i post them here?
If you have sent the information via the Crash Reporter, we will have a copy of everything, but to easily find your crash we will need the Machine ID that pops up in the Crash Reporter. It would also be helpful to know are your pulling the preview via GitHub or through the launcher.
Are you able to reproduce this crash in a blank project or is it specific to your project? If it is specific to your project, make sure that you have your Engine Scalability settings set to EPIC and the Preview Shader Level set to SM5. If you are doing a mobile project please let me know what what Shader MOdel and hardware your are targeting.
I would also attempt to run a verify pass on the engine version from the Launcher which can be done via the Library Section.