Intermittent below error,Let's see the root cause & Fix
Calculation error on quote Q-011232: Error parsing quote: Unexpected token [ in JSON at position 117555
Root Cause : Asynchronous promise method is not returning,return statement was missing in nested method calling.
Fix : Implement correctly the promise chain ,Add the missing return statements,If not returned it will take as undefined and you will get above mentioned defect.
Please refer below QCP GuideLines,Records,Promise Chaining
Observation issue occurs only in Calculate Quote button not in the QLE(Quote Line Editor) Calculate button,Even though from both the places same QCP code executes.Why?
Thanks to Salesforce Support Team for below details.
The Calculate button on the record and within the Quote Line Editor does call the same javascript but it does it in different ways.
When performing a Quote calculation from within the Quote Line Editor the calculation is performed client side, within the web browser,
via javascript.
When the calculation is performed outside of the Quote Line Editor the calculation is enqueues an asynchronous
apex job and the javascript and the calculations take place on the Heroku server.