The errors from the Cloud Pub/Sub Subscription to BigQuery template aren't saved as valid JSON in the PayloadString column and I am unable to replay them.

It looks like this:
{event={userId=1234, sessionEvent={sessionId=DSFG, ua=Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.131 Safari/537.36, browser={name=Chrome, version=74.0.3729.131, major=74}}}

If this is intended, how do I convert it and push it back to Pub/Sub?