I figured out the crash. If you, ALT + TAB and switch to another window, it will trigger a WASM crash during a flight. I tried leaving the sim untouched without switching windows. I kid you not, no more WASM crashes! Try it yourself. I have replicated 3 flights without touching the sim to multitask, no wasm freezes whatsoever!
Downside to this, if you have a single display and use Elevatex or Volanta or even Vatsim Vpilot client, you cannot run windowed mode, else that will trigger a WASM. You must use full screen and NEVER switch to another application during cruise, climb or descent phase.