One of our clients recently upgraded to CiviCRM 4.7.29 and then their existing Contribution page started giving a 500 Server Error.

They asked us to debug and we found that the issue was a missing classname and we traced that to the Pay Later option. Then we found this Pay later not appearing as payment option which looked similar and says it was fixed for CiviCRM 4.7.30.

We upgraded their site and indeed their bug was fixed also.