BackstopJS is throwing "TypeError: selectors.reduce(...).filter is not a function" while while running reference and test

While running the below scenario I have got the error consistently. Even though sufficient delays added.

Trying with the website which has 80% of dynamic content.

Please let me know if any configs to be changed for a web-site.

**Error:
Puppeteer encountered an error while running scenario "Help HomePage"
Error: Evaluation failed: TypeError: selectors.reduce(...).filter is not a function
at Object.expandSelectors (__puppeteer_evaluation_script__:65:16)
at __puppeteer_evaluation_script__:3:62**

Please help in this regard.