The Bing Maps batch geocoding service has a 12 hour SLA, which means that it can take up to 12 hours to process, as noted here: https://learn.microsoft.com/en-us/bingmaps/spatial-data-services/geocode-and-data-source-limits
Errors on the other hand should not occur unless there is an issue with the input file. If you see the job failing repeatedly, please contact the Bing Maps Enterprise support team here https://www.microsoft.com/en-us/maps/support so that they can have the backend team look into this.
To speed up geocoding, you could use the standard geocoding service and make individual geocode requests in parallel. Be sure to limit the frequency of requests to a reasonable limit, I believe there is a limit of 50 request per second from a single IP address for enterprise accounts before rate limiting occurs. If you were to do this at a rate of 25 requests a second, it would take around 34 minutes to process 50K addresses.