Add on simple function error - 'Error Packaging Function. Please try again or contact support for assistance.'

I am receiving the error 'Error Packaging Function. Please try again or contact support for assistance.' when I try to save a simple function within a custom add on. This problem has only recently occurred as I have been able to save functions in the past.

I have tried to save previously working add ons. I have also tried to save functions found in the example add ons (https://github.com/servicem8/addon-sdk-samples). I have also tried clearing my browser cache, cookies, files/images as well as using an incognito window. With the error showing for each.