Error after build that I don't know how to proceed

[chrwei]

I'm using create-react-app if that matters.

I'm only getting this error after I build the project

Code:

react_devtools_backend.js:2430 SyntaxError: Unexpected token u in JSON at position 3
    at JSON.parse (<anonymous>)
    at c (rc-easyui-min.js:10)
    at t.value (rc-easyui-min.js:10)
    at rc-easyui-min.js:10
    at Array.forEach (<anonymous>)
    at t.value (rc-easyui-min.js:10)
    at t.value (rc-easyui-min.js:10)
    at os (react-dom.production.min.js:212)
    at du (react-dom.production.min.js:255)
    at t.unstable_runWithPriority (scheduler.production.min.js:19)

I assume it's something in my data from my api server, but I'm just not finding anything.  Pointing a dev instance at the production api server does not give any errors.

how can figure out exactly what it's having an issue with?

[chrwei]

finally got it, it was my form dynamic rules.

I was ending up with a form rule like ["required", "length[5,undefined]"].  entirely my fault, but very hard to debug.