Not sure hoe helpful this is for debugging, but in testing this a little further and there are some substrings in "accessibility" that throw the 500 error as well:

Fail (500 error):

• a
• acce
• acces
• access
• accessib
• accessibility

Pass (returns):

• ac
• acc
• accessi
• accessibi
• accessibil
• accessibili
• accessibilit

Single letters that throw a 500 error:

• a
• i
• t

Error from the log:

    error: {
      errors: [
        {
          domain: 'global',
          reason: 'invalid',
          message: 'Invalid Value',
          locationType: 'parameter',
          location: 'pageToken'
        }
      ],
      code: 400,
      message: 'Invalid Value'
    }

So far it seems like what's used in a deployment doesn't match code that's used when running things locally. I removed this entire chunk from the handlePage function which handles when the /search page is hit:

Locally I end up with something like this (notice the "hello" in the query params):

But when I deploy the code to a dev environment using gcloud, nothing changes. I still get the 500 error on search terms that I would get it on previously, and I still get search results on terms that worked previously.

@bkjohnson maybe some heavy caching that needs to be cleared out?