Recover from Syntax Error: Error: Missing helper:

[halfnibble]

Whenever a Handlebars exception occurs, e.g.
{{ foo.bar } Note: the missing }
And then a fix is applied, e.g.
{{ foo.bar }}

All custom helpers are gone (deleted and not reloaded), resulting in:
Error: Missing helper:
on page refresh.

Edit: I guess it happens on every change that triggers watch whether or not there is a syntax error.
Edit 2: It appears to be random. It randomly has the custom helper, and randomly does not. Race condition of sorts?