Missing Child Trigger
You’ve probably tried to save a new DLRS and you get an error that looks something like this. “Active: Apex Trigger dlrs_contactTrigger has not been deployed. Click Manage Child Trigger and try again.”
If you are using the Custom Metadata you wont even see the Deploy Child Trigger button until the DLRS record is saved so you might be a bit confused on how do you save if there isn’t even a way to deploy! The easy fix to this is UNCHECK the active box, save the DLRS, deploy the child trigger then edit the DLRS and recheck the active box.
dlrs_CampaignTrigger: execution of AfterUpdate caused by: System.DmlException: Update failed. First exception on row 0 with id 0032w00000X2RxmAAF; first error: INVALID_CROSS_REFERENCE_KEY, invalid cross reference id: [] (dlrs) Trigger.dlrs_CampaignTrigger: line 7, column 1
Error element Update_Account_Name (FlowRecordUpdate). The flow tried to update these records: 5004w00002Kkd0VAAR. This error occurred: CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY: dlrs_CaseTrigger: execution of AfterUpdate caused by: System.SObjectException: Invalid field ActivityDate for Case (dlrs) Trigger.dlrs_CaseTrigger: line 7, column 1.
Old thread but I ran into this problem as well. I think this is the relevant GitHub issue: https://github.com/SFDO-Community/declarative-lookup-rollup-summaries/issues/1203
I posted more details there, but the summary of my workaround was to bypass the problematic Flow(s) when Case status = 'merged'.
Seems like a Winter 24 issue but making the change on the custom metadata record fixed it.