Authentication error caused by changing % to %25 in CSE_ID

[Bestulo]

My CSE_ID contains a % among many numbers, like 09184%3A. This gets changed into URL format into %25, which is how it's logged into the console for the error message, saying that there is a 400 HTTP error, and when I copy the url from the console and use it in the browser, the same happens. If I change the %25 for % in the address, it resolves into the proper image search successfully. I'm going to try to fix this myself on my end, but I think that it would be good if the project code had a fix for it too.

For illustation purposes, I'll leave the JSON response for the error, which is very vague:

{
 "error": {
  "errors": [
   {
    "domain": "global",
    "reason": "invalid",
    "message": "Invalid Value"
   }
  ],
  "code": 400,
  "message": "Invalid Value"
 }
}

(it is explained online that this is may be caused by authentication errors, which is the verfied case here)