Salesforce Non-profit Starter Pack 3.0 Troubleshooting

We have a small non-profit. We use Salesforce NPSP 3.0 to manage our database (1000 contacts). We previously hired a SF expert to customize some functionality (donation processing, etc.). I recently started to receive the error message below. We would like to hire someone to help us fix this issue (and possibly other issues in the future). If you submit a proposal, please include a description of your experience working on similar projects and a rough estimate of how long you estimate you will need to fix the issue. Thank you for your consideration.

=== Error message ===
Salesforce reported the below errors as NPSP was attempting to execute its batch jobs, or at a time when it was unable to display error messages directly to a user. It's likely that NPSP was attempting to update summary fields on Accounts and Contacts, but was unable to save certain records. This failure might have been caused by a variety of issues unrelated to NPSP, such as custom code or validation rules.

Read this article on the Power of Us Hub to learn how these Scheduled Jobs work: https://powerofus.force.com/NPSP_Scheduled_Jobs

If you're not sure how to resolve these errors, post a message in the Nonprofit Success Pack group in the Power of Us Hub: https://powerofus.force.com/HUB_NPSP_Group


Errors:

----------
Error #1:

Error Type: Batch Apex error
Error Date: 2020-03-03 07:01:50
Message: "First error: Attempt to de-reference a null object"
Context: npsp__RD_RecurringDonations_BATCH

Stack Trace:
null