Rollup error after adding a second TypeScript plugin. Can't figure out what I've done wrong

[Sheldonfrith]

I'm getting the following error any time I try to build my project: Cannot find module 'rollupPluginBabelHelpers.js' or its corresponding type declarations.

Here is my 'tsdx.config.js' where I suspect the problem must lie:

const postcss = require('rollup-plugin-postcss');
const transformer =require('ts-type-checked/transformer');
const typescript = require('rollup-plugin-typescript2');

module.exports = {
  rollup(config, options) {
    config.plugins.push(
      typescript({
        transformers: [
          service => ({
            before: [transformer(service.getProgram())],
            after: [],
          }),
        ],
      }),
      postcss({
        config: {
          path: './postcss.config.js',
        },
        extensions: ['.css'],
        minimize: true,
        inject: {
          insertAt: 'top',
        },
      }),
      
    );
    return config;
  },
};

I can't see anything obviously wrong here, but I'm not very familiar with using Rollup (I'm more used to webpack).
Anyone have any suggestions?