BigNumber toFixed throws error causing numbers to appear in scientific notation

[kelsos]

When using the step component on an amount this causes an error and shows scientific notation instead.

TokenInputComponent.html:3 ERROR Error: [BigNumber Error] Argument not a primitive number: 18
    at intCheck (bignumber.js:2789)
    at BigNumber.P.toFixed (bignumber.js:2459)
    at TokenInputComponent.push../src/app/components/token-input/token-input.component.ts.TokenInputComponent.getTokenAmount (token-input.component.ts:216)
    at TokenInputComponent.push../src/app/components/token-input/token-input.component.ts.TokenInputComponent.precise (token-input.component.ts:109)
    at Object.eval [as handleEvent] (TokenInputComponent.html:7)
    at handleEvent (core.js:21673)
    at callWithDebugContext (core.js:22767)
    at Object.debugHandleEvent [as handleEvent] (core.js:22470)
    at dispatchEvent (core.js:19122)
    at core.js:19569

After some investigation it appears that for some reason the _decimals property is a string instead of a number, and this is caused by BatchManager handling all the returned contract values as strings