An error occurred while evaluating expression: record['recordType!****.fields.{***}files']:AC!record.files (Expression evaluation error: RECORD NAME can only be indexed into using square brackets or the index function) (Data Outputs)

Does this mean there is a configuration problem in the process model?

I assume. AC!record.files should more look like AC!record[recordtype!YOUR_TYPE.fields.files].

Check the documentation on how to reference record fields: https://docs.appian.com/suite/help/24.1/reference-records.html

If the problem were related to referencing record  in my interface code, then it would show an error while executing the interface. However, this is not the case. The error only occurs when I click on the button 'inscrire' in my process model. Therefore, I believe the problem lies within the process model.

Otherwise, thank you for the documentation.

Issue is looking like in the below code as you can see, save inside another save function is not valid:

a!save(
local!success,
a!submitUploadedFiles(),
a!save(
ri!record['recordType!{72596258-c9fb-4f4f-a5b7-d2eeb5d31c00}PBY accounts.fields.{33974cb9-8489-4709-afd2-d96a35ec07c6}files'],
fields: {
files: local!file
}
)
),

     /*onSuccess: a!save(*/
            /*local!success, */
            /*a!submitUploadedFiles(),*/
            /*a!save(*/
              /*ri!record['recordType!{72596258-c9fb-4f4f-a5b7-d2eeb5d31c00}PBY accounts.fields.{33974cb9-8489-4709-afd2-d96a35ec07c6}files'],*/
              /*fields: {*/
                /*files: local!file*/
              /*}*/
            /*)*/
          /*),        */
          /*onSuccess: a!save(*/
          /*local!success, */
          /*a!submitUploadedFiles()*/
          /*),*/
/**/
          /*onError: a!save(*/
            /*local!success, */
            /*false*/
          /*)*/
        )