We just updated to 4.7.30 and the latest Drupal 7 version. Now, when viewing participant records that include a contribution record, the following error is in the Fees section:

Sorry, due to an error, we are unable to fulfill your request at the moment. You may want to contact your administrator or service provider with more details about what action you were performing when this occurred. Expected one Contribution but found 0

As far as we can tell, participants are able to register just fine since the update. In the Selections section, the appropriate selections are there, but if we click the Change Selections link, we get the error: Network Error: Unable to reach the server. Please refresh this page in your browser and try again. Refreshing does not help.

We are still able to edit the contribution records that are displayed on the participant record. We can register new participants manually and the error does not appear. The error also seems limited to events...does not appear in membership.

We have no Civi Extensions on this site.