A system admin encounters an error at run time that a record update failed when...

A runtime error during a Customizable Rollup operation often occurs if the target field has an active validation rule that prevents the update. Validation rules enforce specific criteria that records must meet before they can be saved, and if these criteria are not met during the rollup operation, an error will occur.

Steps to Troubleshoot:

Review Validation Rules:

Navigate to Setup -> Object Manager -> [Target Object] -> Validation Rules.

Review the validation rules on the target object to identify any that might conflict with the rollup operation.

Modify or Temporarily Disable Validation Rules:

If a validation rule is causing the error, consider modifying the rule to accommodate the rollup operation or temporarily disabling it during the data update process.

Check Rollup Configuration:

Ensure the Customizable Rollup settings are correctly configured and that no unnecessary constraints are in place.