Now apparently \r, \b, \t, \f, etc aren't the only problematic chars that can give you this error.
Note that some browsers may have additional requirements for the input of JSON.parse.
Run this test code on your browser:
var arr = [];
for(var x=0; x < 0xffff; ++x){
try{
JSON.parse(String.fromCharCode(0x22, x, 0x22));
}catch(e){
arr.push(x);
}
}
console.log(arr);
Testing on Chrome, I see that it doesn't allow JSON.parse(String.fromCharCode(0x22, x, 0x22)); where x is 34, 92, or from 0 to 31.
Chars 34 and 92 are the " and \ characters respectively, and they are usually expected and properly escaped. It's chars 0 to 31 that would give you problems.
To help with debugging, before you do JSON.parse(input), first verify that the input doesn't contain problematic characters:
function VerifyInput(input){
for(var x=0; x<input.length; ++x){
let c = input.charCodeAt(x);
if(c >= 0 && c <= 31){
throw 'problematic character found at position ' + x;
}
}
}