yarn dev doesnt work, but yarn start does

[oscareawork]

I cloned, and ran "yarn" to install. I then try "yarn dev" and it fails to launch with this:

`yarn run v1.22.4
$ cross-env START_HOT=1 node -r @babel/register ./internals/scripts/check-port-in-use.js && cross-env START_HOT=1 yarn start-renderer-dev
$ cross-env NODE_ENV=development webpack-dev-server --config configs/webpack.config.renderer.dev.babel.js
Starting Main Process...

[email protected] start-main-dev /Users/oscar-work/dev/cgen
cross-env HOT=1 NODE_ENV=development electron -r @babel/register ./app/main.dev.js

(node:14911) UnhandledPromiseRejectionWarning: Error: Exited with code 9
at ChildProcess. (/Users/oscar-work/dev/cgen/node_modules/cross-unzip/index.js:38:21)
at ChildProcess.emit (events.js:194:13)
at Process.ChildProcess._handle.onexit (internal/child_process.js:254:12)
(node:14911) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:14911) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.`

However, yarn start loads fine (but of course, I cannot develop on it since it doesnt hot-reload changes). Any ideas? I am on the latest MacOS Catalina.