We can't save this record because the "ABC" process failed [CANNOT_EXECUTE_FLOW_TRIGGER]

This is another error which is specific to your Org. The error will specify the name of the Process which has failed e.g. "Account Insert Flow". The error occurs because the job that you have run e.g. Inserting new Accounts has triggered a process in Salesforce to run which has subsequently failed.

E2120 - ECE_SForceUpdateInsert: We got an error back from SalesForce when trying to update or insert data in SalesForce. Error returned from SFDC on upsert: [message: We can't save this record because the Update Sale Summary process failed. Give your Salesforce admin these details.

In this case, you would need to check your current flows in Salesforce, check the reason why it failed and adjust it accordingly.