Ionic 2 project working fine in browser but will not build for IOS

Hopefully someone can help, pulling my hair out on this one a little.

I am developing an app ionic 2 with firebase 3 backend. It works fine when tested locally in the browser, i.e. when I run the command:

ionic serve

I had no problem getting it on to my IOS device previously, however I am now continuously getting the following error when I try to build:

myIonicFFApp $ ionic build ios

Running 'build:before' npm script before build

> Feetfirst@ build /Users/alan/Desktop/myIonicFFApp

> ionic-app-scripts build

[10:38:00]  ionic-app-scripts 0.0.37 

[10:38:00]  build prod started ... 

[10:38:00]  clean started ... 

[10:38:00]  clean finished in 3 ms 
[10:38:00]  copy started ... 
[10:38:00]  ngc started ... 
[10:38:01]  copy finished in 109 ms 
[10:38:01]  lint started ... 
[10:38:03]  lint finished in 1.90 s 
[10:38:13]  Error: Error at /Users/alan/Desktop/myIonicFFApp/.tmp/pages/infant-create/infant-create.ngfactory.ts:437:40 

[10:38:13]  Property 'infantName' does not exist on type 'InfantCreatePage'. 
[10:38:13]  Error at /Users/alan/Desktop/myIonicFFApp/.tmp/pages/infant-create/infant-create.ngfactory.ts:467:41 
[10:38:13]  Property 'infantDate' does not exist on type 'InfantCreatePage'. 
[10:38:13]  Error at /Users/alan/Desktop/myIonicFFApp/.tmp/pages/infant-create/infant-create.ngfactory.ts:603:43 
[10:38:13]  Property 'infantName' does not exist on type 'InfantCreatePage'. 
[10:38:13]  Error at /Users/alan/Desktop/myIonicFFApp/.tmp/pages/infant-create/infant-create.ngfactory.ts:608:43 

[10:38:13]  Property 'infantDate' does not exist on type 'InfantCreatePage'. 

[10:38:13]  Error at /Users/alan/Desktop/myIonicFFApp/.tmp/pages/infant-create/infant-create.ngfactory.ts:623:68 
[10:38:13]  Property 'infantName' does not exist on type 'InfantCreatePage'. 

[10:38:13]  Error at /Users/alan/Desktop/myIonicFFApp/.tmp/pages/infant-create/infant-create.ngfactory.ts:623:92 
[10:38:13]  Property 'infantDate' does not exist on type 'InfantCreatePage'. 

[10:38:13]  ngc failed 

[10:38:13]  ionic-app-script task: "build" 

[10:38:13]  Error: Error 



npm ERR! Darwin 16.0.0

npm ERR! argv "/usr/local/bin/node" "/usr/local/bin/npm" "run" "build"
npm ERR! node v4.4.5
npm ERR! npm  v3.10.8
npm ERR! code ELIFECYCLE
npm ERR! Feetfirst@ build: `ionic-app-scripts build`
npm ERR! Exit status 1
npm ERR! 

npm ERR! Failed at the Feetfirst@ build script 'ionic-app-scripts build'.
npm ERR! Make sure you have the latest version of node.js and npm installed.
npm ERR! If you do, this is most likely a problem with the Feetfirst     package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm 
ERR!     ionic-app-scripts build
npm ERR! You can get information on how to open an issue for this project with:

npm ERR!     npm bugs Feetfirst
npm ERR!  Or if that isn't available, you can get their info via:
npm ERR!     npm owner ls Feetfirst
npm ERR!  There is likely additional logging output above.

npm ERR! Please include the following file with any support request:
npm ERR!     /Users/alan/Desktop/myIonicFFApp/npm-debug.log

Caught exception:
 undefined 

Any ideas what might cause this?

Hard for anybody to say without seeing the code of InfantCreatePage, but perhaps a private property trying to be accessed from a template?