Thank you Sam
found the solution here https://github.com/eouia/MMM-AssistantMk2/issues/231
MM has stopped crashing.
Greg

I have exactly the same problem. When triggering MK2 Assistant with hotword or with mouse click, MM crashes with the following errors:

[AMK2] Recipe is loaded: hide_and_show_all_modules.js
[AMK2] Recipe is loaded: reboot.js
[AMK2] Recipe is loaded: screen_onoff.js
[AMK2] Recipe is loaded: shutdown.js
[AMK2] Temporal storage directory is clearing.
[HOTWORD] begins.
[HOTWORD] Detector starts listening.
[HOTWORD] stops.
[HOTWORD] Final Result: { detected: false }
[HOTWORD] begins.
[HOTWORD] Detector starts listening.
[AMK2] assistant ready
/home/pi/MagicMirror/node_modules/electron/dist/electron js/electron.js: symbol lookup error: /home/pi/MagicMirror/modules/MMM-AssistantMk2/node_modules/grpc/src/node/extension_binary/electron-v3.0-linux-arm-glibc/grpc_node.node: undefined symbol: __atomic_store_8
npm ERR! file sh
npm ERR! code ELIFECYCLE
npm ERR! errno ENOENT
npm ERR! syscall spawn
npm ERR! magicmirror@2.9.0 start: sh run-start.sh
npm ERR! spawn ENOENT
npm ERR!
npm ERR! Failed at the magicmirror@2.9.0 start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR! /home/pi/.npm/_logs/2019-10-29T22_08_07_413Z-debug.log