Gulp crashes after upgrading to Catalina


New user here! So apologies in advance.

I upgraded the Mac I use for my development to Catalina 2 days ago, yesterday when I open Hyper it asked me to change to zsh. Not really know why, I did so! 

Today when I try to run some bash scripts, the environment doesn’t see them. After a bit of googling I changed it back to bash. Tried my aslias again (so) and it doesn’t see it.

I’ve not change directory into where I run my gulp from and I now get the error(s):

@RetinaMac Stand Out Property Manager % gulp
[08:58:07] Using gulpfile ~/Git/Stand Out Property Manager/gulpfile.js
gulpInst.start.apply(gulpInst, toRun);

TypeError: Cannot read property ‘apply’ of undefined
at /usr/local/lib/node_modules/gulp/bin/gulp.js:129:20
at internalTickCallback (internal/process/next_tick.js:70:11)
at process._tickCallback (internal/process/next_tick.js:47:5)
at Function.Module.runMain (internal/modules/cjs/loader.js:777:11)
at executeUserCode (internal/bootstrap/node.js:342:17)
at startExecution (internal/bootstrap/node.js:276:5)
at startup (internal/bootstrap/node.js:227:5)
at bootstrapNodeJSCore (internal/bootstrap/node.js:743:3)

Any idea of what I need to do to fix the error (other than inventing a time machine and rolling back my os to previous version!).

Cheers in advance